APEB Journal

Introduction

In recent years, there has been increasing concern over public health threated presented by introduction of petroleum hydrocarbon pollutants in environment due to anthropogenic activities to a greater extent and natural process to less extent [1].

The rapid economic growth achieved in last decade has been paralled by an increase in global petroleum oil consumption [2] in which different petroleum oil industries such as fuel are fast growing, synthetic polymers and petrochemicals. Polycyclic Aromatic Hydrocarbons (PAHs) are category of over 100 various, compounds released from incomplete combustion source[3].These sources are either natural i.e. petroleum industry activities as well as accidental spills, bush fire, forest and volcanoes eruptions or manmade combustion i.e. care emission, cigarette smoke, wood burning and combustion of dung and crop residues [4-6].

PAHs are a group of hydrophobic hydro carbonic compounds consisting of two or more combined benzene rings in linear, angular or cluster arrangement[7-9]. Most of PAHs persist in the ecosystem for many years owing to their hydrophobicity and their absorption to solid particles[10,11].

Physical and chemical properties of PAHs

PAHs are organic substance made up of carbon and hydrogen they can be divided into two categories: Low Molecular Weight (LMW-PAHs) compounds consisting of fewer than four rings and High Molecular Weight (HMW-PAHs) compounds of four or more rings. Pure PAHs are usually colored crystalline solids at ambient temperature [12].Chemical structures of some commonly PAHs are indicated in Figure 1.

Physical and chemical characteristics of some priority PAHs listed by the USEPA are shown in Table 1.

PAHs possess very characteristic UV absorbance spectra. As each ring structure has unique UV. Spectrum, each isomer exhibits a unique absorbance spectrum also. This is especially useful in identification of PAHs [19].

Regarding to the mutagenic and carcinogenic effects from chronic exposure to PAHs and their metabolites classifications as enlisted by US. Department of Health and Human Services (HHS), International Agency for Research on Cancer (IARC, 2009)[20]and US. Environmental protection Agency (USEPA, 2007)[21] are indicated in Table 2.

Pad impact of PAHs on human

PAHs pose high risks on human populations[22,23].United State Environmental protection Agency (USEPA) has enlisted 16 of PAHs as priority pollutants[21]. PAHs have a potential to induce malignant tumors that primarily affect skin and other epithelial tissue as they have a great affinity for nucleophilic center of macromolecules like RNA, protein and DNA[24].

PAHs induce Geno toxicity, mutagenicity and carcinogenicity as shown in different living organisms or cell lines [24,25-27].PAHs are environmental carcinogens[28], associated with skin, lung, pharynx, oral and other cancers [29].

Galicia, eye redness, headache, sore throat, trauma, nausea, dizziness, breathing difficulty and abdominal pain have been reported[30]. Lung cancer is expected to cause 10 million deaths per year worldwide by near 2030[31],also PAH-DNA adducts have been detected in blood from newborns whose mothers were living in polluted sites[32].PAHs from stable and depurating DNA adducts in mouse skin to induce paraneoplastic mutations. Depurating adducts play a major role in forming tumorigenic mutations[33].A number of PAHs found in cigarette smoke of US and European brands, such as Benz[a]-anthracene and Benz [a]-Pyrene have been classified as carcinogens by the International Agency for Research on cancer[34], causing lung cancer mortality[35-37].

Epidemiological studies have shown evidence that cancer, birth defects, genetic damage[20], immunodeficiency[21], respiratory [38] and nervous system disorders [21] can be linked to exposure to occupational levels of PAHs.

PAHs are rapidly distributed in wide variety of tissues with a marked tendency for localization in body fat. Metabolism of PAHs occurs via cytochrome P460-mediated mixed function oxidase systems with oxidation or hydroxylation as first step[22]. Due to lipophilic characteristics of PAHs they tend to accumulate in food chain[39].PAHs are able to cross placental barrier and are also found in breast milk[40].High prenatal exposure to PAHs is associated with low IQ at age three, increased behavioral problems at age six to eight and childhood asthma[41,42].Furthermore associated with reduced birth weight, length and head circumference, lower scores on childhood tests of neurodevelopment and with symptoms of anxious / depressed and attention problems[43].

Once PAHs enter the human body, PAHs are metabolized in a number of organs and excreted in bile and urine also excreted in breast milk and stored in adipose tissue[44].Pyrene is commonly found in PAH mixtures, and its urinary metabolite, 1-hydroxypyrene, has been used as an indicator of exposure to PAH chemicals [45-49].

Physicochemical degradation of PAHs

Many conventional engineering based physicochemical decontamination methods are expensive due to the cost of excavation and transportation of large quantities of contaminated materials for ex-situ treatment viz soil washing, chemical inactivation (use potassium permanganate and/ or hydrogen peroxide as a chemical oxidant to mineralize non-aqueous contaminants such as petroleum) and incineration[50-52].Among physicochemical methods used for PAHs treatment, are dispersion dilution, sorption, volatilization and abiotic transformation[53,54].

There are another chemical methods e.g, chemical oxidation and photocatalysis remediation[55,56].Due to the increasing cost and limited efficiency of these conventional physicochemical treatments obligatory development of alternative technology for insitu application must be created, particularly based on microbial remendation capabilities of microorganisms [51,57].

Microbial degradation of PAHs

Microbial degradation is green technology for cleanup of pollutants by biological means include bioremediation, biodegradation, bio-augmentation, biostimulation and phytoremediation[58-62].

Microorganisms play crucial role in maintaining ecosystem and biosphere to develop sustainable environmental cleaning up [52]. They also used to mitigate adverse effects of pollutants [54,63,64].Bacteria, fungi and alge are reported to be hydrocarbon pollutants degraders [53,65-69].

Resistance of hydrocarbon pollutants to microbial degradation in either soil or water tends to increase with the type as well as molecular weight and number of rings. Naphthalene is ready biodegraded in most situations, however PAHs with four, five or six rings tend to be degraded much more slowly. Generally aerobic biodegradation occurs much more rapidly than anaerobic biodegradation[70].

Polycyclic aromatic hydrocarbons (PAHs) degrading bacteria

A large number of bacteria that metabolize PAHs have been isolated (Alcaligenes dentrificans, Rhodococcus sp., Pseudomonas sp., Mycobacterium sp.) [71].A variety of bacteria can degrade certain PAHs completely to CO₂ and metabolic intermediates or H2O[72]. Mycobacterium spp. Sphingomonas spp., Rhodococcus spp. and Nocardia spp. populations were selectively stimulated in soil contaminated with PAHs or hexadecane[73].

Low Molecular weight PAHs (LM W-PAHs) degrading bacteria

A large number of naphthalene-degrading bacteria including Pseudomonaspanipatensis ; Pseudomonas putida; P. vesicularis; P. paucimobilis; Bacillus cereus; Mycobacterium sp.; Alcaligenes dentrificans; Rhodococcus sp.; Corynebacterium venale; Cyclotrophicus sp.; Streptomyces sp.; Vibro sp. and Bordetella avium. Have been isolated[68,74].In case of naphthalene-degrading bacteria, a different bacteria including Arthrobacter polychromogenes; Aeromonas sp.; Beijerincka sp.;Micrococcus sp. Alcaligenes faecalis; Mycobacterium sp.;Nocardia sp.; Bordetella sp.; Flavobacterium sp.Bacillus sp.; Vibro sp. and Rhodococcus sp.[69].The degrading bacterial strains that have been characterized are taxonomically diverse and mainly belong to the genera Mycobacterium,Pseudomonas, Bacillus, Sphingomonas, and Alcaligenes.[67,75-78].Bacillus subtilis showed the highest catechol, 1, 2 dioxygenase activity in MSM supplemented with anthracene with 99% degradation after five days incubation [79].

High Molecular weight PAHs (HM W-PAHs) degrading bacteria

Sphingobium KK22 isolated from soil of Texas, USA. This strain able to grow on phenanthrene and metabolize Benzo[a]anthracene[80]. Mycobacterium RJG II-135 is capable to degrade phenanthrene, anthracene and pyrene at 10 to 20 fold greater than Benzo[a]anthracene and Benzo[a]pyrene [81]. Mycobacterium vanbaalenii PYR-1 is able also to degrade wide range of low and high molecular weight of PAHs [82]. Bacillus subtilis isolated from contaminated soil with PAHs. Bacillus subtilis is able to transform pyrene and Benzo[a]pyrene, but degradation rate of Benzo[a]pyrene is greater than Pyrene [83].

Two microorganisms Bacillus SPO2 and Mucur SFO6 which are capable to degrade PAHs, were immobilized on vermiculite and investigate their ability to degrade Benzo[a]pyrene. Removal rate in case of immobilized bacterial-fungal mixed consortium was higher than that of freely mobile mixed consortium [84].In another research, Bacillus subtilis DM-04 and Pseudomonas aeruginosa mucoid (M) and Non-Mucoid (NM) strains isolated from petroleum contaminated soil samples of North East India were used to degrade pyrene. Bacillus subtilis showed higher utilization of pyrene than Pseudomonas.

Bacillus subtilis and Pseudomonas were able to secreting biosurfactants in the medium which enhanced the solubility of pyrene in aqueous media leading to higher utilization of pyrene [85].Bacterial consortium CON-3, isolated from crude oil contaminated soil of Punjab, India cometabolized 50 μg/ml pyrene in the presence of glucose (0.5% w/v) at 30 o C. Bacillus PK-12, Bacillus PK-13 and Bacillus PK-14 from CON-3 were able cometabolize pyrene in order PK-12> PK-13> PK-14 after 35 days of incubation [86].Also in India, a bacterial strain Bacillus thuringiensis NA2 was isolated from polluted site with petroleum oil. Bacillus thuringiensis was able to degrade fluoranthene and pyrene. By optimizing the different factors (PH, Temperature, glucose addition etc…) which increased the biodegradation [87]. Syakti et.al., (2013)[88] isolated 6 viable and cultural bacterial strains from contaminated mangroves. The bacterial strains were identified by 16S RNA as Bacillus aquimaris, Bacillus megterium and Bacillus pumilus while the other 3 strains were related to Flexibacteraceae bacterium, Halobacilus trueperi and Rhodobacteraceae bacterium. These strains were able to grow on PAHs (Phenothiazine, fluorine, fluornthene, dibenzothiophene, phenantherene and pyrene). Combination of two bacteria, Bacillus PY-1 and Sphingomonas PY-2 and a fungus Fusarium Py-3 isolated from contaminated soils were able to degrade pyrene and volatize arsenic independently and in combination. Removal of pyrene in high rate was recorded after 9 days in liquid medium and 63 days in soil [89]. Abo-State et.al., (2013,2014) [90,91] isolated five bacterial strains from soil and water contaminated with petroleum oil, Cairo, Egypt. The most potent strains (two strains) were identified by16S rRNA as Bacillus amyloliquifaciens MAM-62 with accession number 038054 and the other bacterial strain was Achromobacter xylosoxidans MAM-29 with accession number 038055.Both of the two bacterial strains were able to degrade pyrene efficiently as a sole carbon and energy source.

Bacillus amyloliquifaciens MAM-62 degrade 94.1%; 90.8%; 90.6; 72.9% and 51.4% of 100,200, 300, 400, and 500 μg/l pyrene after 21 days respectively[91].

However A. xylosoxidans MAM-29 degraded 95.0%; 90.5%;90.30%; 71.1% and 50.7% of the Benzo[a]anthracene as same pyrene concentrations respectively[92]. However, [67]isolated eight bacterial strains from soil contaminated with crude petroleum oil from Egypt. The most potant bacterial strain, isolateMAM-P8 was identified by 16Sr RNA as Bacillus altitudinis which was able todegrade 91%,, 33% and 97% of PAHs mixture (500 μM pyrene, 500 μM Benzo [a] anthracene and 50 μM Benzo [a] pyrene) respectively.

Pseudomonas aeruginosaSP4 isolated from contaminated soil produce surfactant, by enhancing biosurfactant production for more efficient pyrene degradation[93].

Pseudomonas isolate PAHs As-1removed all 60 mgl^l-phenanthrene and half of 20 mg^l-1pyrene within 60 h respectively[94].Brevibacillus brevis adsorbed pyrene initially on their cells and then pyrene was transported and intracellularly degraded. The removal of pyrene (mgl^l-) was 0.75 mg^l-after 168 hours. PAHs-utilizing bacteria (26) were isolated from soil of 7 sites of Mathura refinery, India. The most potant strains were 15 strains (Bacillus, Acinetobacter, Stenotraphomonas, Alcaligenes, Lysinibacillus, Brevibacterium, Serratia and Streptomyces were adapted to utilize mixture of 4 PAHs (anthracene, fluorine, phenanthrene and pyrene). A cosortium of 4 most potant isolates were able to degrade PAHs more efficiently within 7 days[95].

In case of Stenotrophomonas maltophilia BR12 which was isolated from oil-contaminated soil in India, it was able to grow best at 50 μgml-1pyrene and degrade nearly 100% of pyrene after 20 days and produce high amount of surfactant[96].

A batch culture of Proteus vulgaris CPY1and Pseudomonas aeruginosa LPY1 on 100 mgl^-1pyrene degrade nearly complete degradation[97].Pyrene and anthracene utilizing bacteria isolated from water used engine oil contaminated soil from Malaysia. Thirteen different bacterial species were isolated including Bacillusthuringiensis and Bacillus megaterium, Salmonella enterica and Bacillus toyonesis. All isolates degraded within 7 days almost all PAHs [98].

Degradation of LMW-PAHs by the marine halotolerant Achromobacter xylosoxidans have been determined. Glucose in combination with a triton x-100 and b-cyclodextrine resulted in 2.8 and 1.4 fold increasing in degradation of LMW-PAHs and 7.59 and 2.23 fold increase in degradation of HMW-PAHs respectively[99]. Mycobacterium gilvum strain PYR-GCK isolated from an estuary polluted with PAHs and was able to degrade pyrene efficiently [100].

Consortium Y-12 isolated from soil sample in Haikou city, China was able to degrade a mixture of PAHs including phenanthrene, Anthracene, fluoranthene, pyrene and Benz[a]pyrene. A bacterial strain was isolated from consortium Y-12 and identified by 16S rRNA as Sphingobium sp.FB3 [101].

Staphylococcus was isolated from diesel contaminated soil sample and identified by 16S rRNA as Staphylococcus nepalensis which was able to degrade pyrene at PH8 and 30°C within 5 days incubation. The best bacterial growth and efficient pyrene degradation have been recorded with Co-substrate (glucose 4% and sucrose 2%) were added [102].

It was shown that mono culture of Pseudomonas monteilii P26 and Pseudomonas sp. number 3 could degrade efficiently LMW-PAHs but did not show interesting HMW-PAHs removal capabilities whereas, the Actinobacteria rodococcus p18, Gardonia H 19 and Rhodococcus F27 were able to degrade efficiently HMW-PAHs, but they did not remove LMW-PAHs from culture medium. The combination of four of these five strains (called C15 mixed culture) removed naphthalene and phenanthrene completely, and showed the highest pyrene biodegradation activity with removal values close to half, almost 6 times higher than those values recorded with strains in pure culture[103].

The degradation rates of consortium to pyrene and fluoranthene increased compare to pure culture of PY97M [104].Main while Pyrene was used as sole carbon energy source by isolated strain of Pseudomonas JPYR-1 and the maximum pyrene degradation rate was 3.07 mgml^-1h^-1 in 48 h. incubation with initial pyrene concentration of 200 μg/ml^-1[105].But in case of pyrene-degrading endophytic bacterium, Staphylococcus BJ06, this strain was capable to degrade pyrene 50 μg/ml^-1[106].

Pyrene can be degraded by functional strain F14 which was constructed through protoplast fusion between Sphingomonas GY2B and Pseudomonas GP3A.The degradation of Pyrene by F14 was increased as concentration of pyrene decreased from 100μg/ml^-1to 15 μg/ml^-1within 10 days. Pyrene when it was in binary mixture with naphthalene or phenanthracene, Pyrene degradation was enhanced but more efficient naphthalene have been recorded than that of phenanthracene. The enzymatic activity of binding efficiency of Actinobacter radioresistens deoxygenase with chrysene is lesser binding energy than benzo[a]Pyrene while in case of Rhodococcus opacusbenzo[a]Pyrene binds with lesser binding energy as compared to chrysene [107].

Four strains that could degrade both LMW-PAHs and HMW-PAHs were isolated from long-term manufacture gas plant site soil. These isolates included Stenotrophomonas(MTS-2), Citrobacter (MTS-3) and the most efficient isolate was Pseudomonas(MTS-1) in degradation of HMW-PAHs[108].

The bacterial strains Burkholderia fungorum T3A13001 and CaulobacterT2A12002 were pyrene degraders. Caulobacter sp, degraded 21% and 24% of Pyrene at 9.0 pH and 5.0 respectively, while B. fungorum was active in a wide range of pH values[109]. Main while a new halophilic bacterium capable of degrading HMW-PAHs were isolated from costal soil of the yellow sea, China. This bacterium was identified by 16S rRNA as Thalassospira TSL5-1. The Pyrene degradation occurred at salinity ranging from 0.5% to 19.5% with optimal value between 3.5% and 5% and degradation of Pyrene influenced greatly by pH values [110].Twenty one isolates from human skin having abilities to degrade benzo[a]Pyrene have been isolated and characterized. Benzo[a]Pyrene was completely degraded by at least 4 isolates. These isolates included Gram positive and Gram negative with micrococci being predominant[111].

A novel strain of Bacillus BMT4i capable of utilize Benzo[a]Pyrene as a sole carbon and energy source via enducible chromosomally encoded pathway was isolated. This strain was improved by inducing random mutations through treating by physical mutagen (UV) or chemical mutagen (ethyle methyl sulphonate [EMS], 5-bromouracil [5BU] and Acridine Orange [AO]). It was found that a UV-mutant (BMT4imuv2) exhibited higher Benzo[a]Pyrene degradation when compared with the wild type[112,113].Also, nine bacterial strains capable of degrading Benzo[a]Pyrene were isolated from Tokyo Bay and Tama River in Japan. The isolates belonged to the phyla Proteobacteria, Actinobacteria, Bacteroidetes and firmicutes. Isolate IT B II was identified by 16SrRNA as Mesoflavibacter zeaxanthinifaciens. This strain utilize Benzo[a]Pyrene as a sole carbon and energy source[114].

Over 33 days pyrene sorbed on hydrophobic filters more than half of pyrene than the five ring Benzo[a]pyrene and Benzo[a]fluoranthene by microbes having the ability to specialize in adhesion. Most bacteria enriched by HMW-PAHs were Bacillus, Mycobacterium and Pseudomonas [115].

Enzymes and genes involved in PAHs-degradation

Enzymes play an important role in microbial degradation of PAHs, oil, fuel activities and many other compounds[116].

Oxidoreductase are enzymes that clear chemical bonds and transfer the electrons from the reduced organic substrate (donner) to another chemical compound (acceptor). During these oxidation reduction reaction, contaminants are oxidized to harmless compounds. Oxygenases classified under the oxidoreductase group of enzymes [117].Oxidation reaction is the major enzymatic reaction of aerobic biodegradation is catalyzed by oxygenases.

Oxygenases metabolize organic compounds, they increased their reactivity, water solubility and cleave the organic ring[118].On the bases of the number of oxygen atoms used for oxidation, oxygenases can be further divided into two groups:I) Monooxygenases and II) Dioxgenases.

Monooxygenases transfer one atom of molecular oxygen to the organic compound and they possess highly region selectivity and steroselectivity on a wide range of substrates[118].The members of the genus Pseudomonas are known to have diverse metabolic pathways and grow using different substrates as a source of carbon example Pseudomonas aeruginosa N7B1 [119]. Pseudomonas stutzeri produce catechol 2, 3 dioxygenase responsible for Meta cleavage of catechol[120].

PAH-induced proteins of Mycobacterium vanbaalenii PYR-1 grown on pyrene are catalase-peroxidase, putative monooxygenase, dioxygenase small subunit, and small subunit of naphthalene induced dioxygenase and aldehyde dehydrogenase. Main while carbohydrate metabolism related proteins are enolase, 6-phosphogluconate dehydrogenase, indol-3-glycerol phosphate synthase and fumarase[121]. Several Mycobacterium spp. having multiple dioxygenase [122-124].The genes designated mid A3B3 encoding the subunits of terminal dioxygenase detected enzyme of Mycobacterium vanbaalenii PYR-1 showed a close similarities to PAH-ring hydroxylating dioxydenases from Mycobacterium and Rhodococcus spp. but has a highest similarity to α-subunit of Nocardioides KP7 fumarase [82].

The NahAc gene was detected in 13 Gram-negative isolates and sequence of Nah Ac-like genes were obtained from Pseudomonas brenneri, Enterobacter, Pseudomonas entomophila, Pseudomonas koreensis and Stenotrophomonas strains[125].

Four aromatic ring cleavage dioxygenase genes: Phd F, Phd I, Pea G and Pca H critical to pyrene biodegradation were detected in Mycobacterium gilvum PYR-GCK[100].

Microbacterium BPW, Novosphingobium PCY, Ralstonia BPH, Alcaligenes SSKIB and Achromobacter SSK4 were isolated from mangrove sediment.These strains degrade more than 50% of 100 ugml^-1of phenanthracene within 2 weeks. Strains PCY and BPW degrade 100% pyrene. The presence of α- subunit of pyrene dioxygenase gene (nidA) in Ph/pyrene degrading ability[126].

In Korea, sediment of U involved San Bay, a marine bacterium Novosphingobium pentaromativorans sp. US6-1was able to degrade PAHs. Various enzymes including PAH ring hydroxylating dioxygenase α- subunit (RHD α), 4-hydoxybenzoate3-monooxygenase and salicylaldehyde dehydrogenase were associated with PAHs degradation.

Strain US6-1 degrade PAHs via a metabolic route initiated by RHDα and that degradation occurred via salicylate pathway or phatholate pathway. Both of them inter TCA cycle and were mineralized to CO₂ and H₂O[127-129].

A strategy based on selection of Mycobacterium vanbaalenii PYR-1 mutant (6GII) that degrades HMW-PAHs but not LMW-PAHs. This mutant was defective inPdoA2 gene encoding an aromatic Ring Hydroxylating Oxygenase [RHO] enzyme. Mutant (6GII) had lower rate of fluorine, anthracene and pyrene degradation[130].Hydrocarbon catabolic genes from 9 different locations around Syowa station, Antarctica have been determined. PAH-ring-hydroxylating dioxygenase coding genes from Gram +ve and Gm –ve bacteria were detected.

Benzo[a]pyrene metabolism involved two transcripts that encode a putative Dsz A/ NtaA like monooxygenase and NifH-like reductase respectively [111].

RHD genes in clone libraries of Gram +ve were releated to I) nid A3 of Mycobacterium Py146, II) Pdo A of Terrabacterium HH4, III) Mid A of Diaphorobacter KOTLB and IV) Pdo A2 of Mycobacterium CH-2. While that of Gram –Ve, RHD geneswere related to I) Naphthalene dioxygenase of Burkholderia glathei II) Phn Ac of Burkholderia satisoli and III) RHD α- subunit of uncultured bacterium [131].

From costal environment a close to Burkholderia fungorum and Mycobacterium gilvum had mid A, mid A3, Pdo A2 and PCaH genes [132].

The ring-hydroxylating dioxygenase RHDase coding for RHDases and 1-hydroxy 2- naphthoate dioxygenase 1H2Dase genes coding for 1H2Dase enzymes play importantroles in decomposing the intermediates of PAHs which can be separated from Arthrobacter sp. SAO₂ and have the capacity of degrading phenanthrene [133].Liang et al., (2019 a, b) [134,135] used for first time gene - targeted metagenomics to investigate the diversity of PAH- degrading bacterial communities in oil field soils and mangrove sediments. A PAH hydratase - aldolase - encoding gene Pah E was a superior biomarker for PAH - degrading bacteria instead of Pah Ac which encoded the alfa - subunit of PAH ring -hydroxylating dioxygenase as functional marker gene.

Bacterial degradation pathways of PAHs

Biodegradation of pollutant involves series of steps using different enzymes [65]. Hydrocarbons can selectively be metabolized by individual strain of microorganism or consortium of microbial strains belong to either the same or different genera [64,90]However, consortium have been proved to be more efficient than individual cultures for metabolizing or biodegrading pollutants [136-139].

Initial oxidative attack followed by ring cleavage of benzene ring is the key step in degradation of aromatics and polycyclic aromatic hydrocarbons (PAHs) which normally involves diol formation followed by ring cleavage and formation of dicarboxylic acid[140].

First step in the microbial degradation of PAHs is oxidation catalyzed by monooxygenase or dioxygenase[141], which introduces atom of oxygen at two carbon atoms of benzene ring resulted in the formation of cis-dihydrodiol[142,143].Aerobic catabolic pathway involves a wide variety of peripheral degradation pathways whichtransform PAHs into small number of intermediates that enter the Tricarboxylic Acid (TCA) cycle[144].

Synthesis of cell biomass formed from central precursor metabolites (Succinate, Acetyl co A, Pyruvate, and Gluconeogenesis) which resulted in synthesis of sugars and growth [116].

The most common way of initial oxidation is formation a diol, followed by ring cleavage and formation of dicarboxylic acid [143]and formation of Cis-dihydrodiols by incorporation of both oxygen atoms of an oxygen molecule and then formation of catecols. Ortho- or meta-cleavage pathway lead to formation of central intermediates (e.g.: Protocatechuates and caticols with further steps converted to TCA cycle intermediates[65].Anaerobic degradation is more recent as compared to aerobic degradation [145].This is due to less information is available about the genes and enzymes involved in these pathways[146].

Naphthalene degradation pathways:-

Naphthalene has low water solubility and high solid-liquid distribution ratio [147].Salicylic acid is an intermediate compound formed in microbial pathway of naphthalene degradation as shown in Figure 2[148]by Pseudomonas putida.

Streptomyces griseus catalyze the biotransformation of naphthalene to 4-hydroxy-1tetralone in good yield, 2-methyl-1, 4-naphoquinone and 2-methyl-4-hydroxy-1 tetralone as indicated in Figure 3 [149].

Degradation of naphthalene starts through the multi- component enzyme naphthalene dioxygenase, which converts naphthalene to Cis-naphthalene dihydrodiol. This diol is transformed to 1, 2-dihydroxynaphthalene via the enzyme Cis-dihydrodiol dehydrogenase. At this point two pathways are possible Figure 4. The ring fission of 1, 2-dihydroxynaphthalene leads to the formation of O-phthalic pathway) which is subsequently converted to intermediates enter the Krebs Cycle (TCA) or the formation of salicylates (Salicylic pathway) and also enter TCA cycle [150,151].In the second pathway, 1, 2-dihydroxy naphthalene is converted to salicylate which is either transformed to caticol or gentisate (salicylic pathway). The plasmid possess degradative genes have been detected in several bacterial species including the plasmid NAH7 of Pseudomonas putida strain G [152]and that of strain Ak5 and plasmid of Gordonia sp. strain CC-NAPH129-6[153].Hydroxy-phthalic acid is an intermediate arising after O-phthalic have been identified in Pseudomonas aeruginosa but not found in M. radiotolerans O-phthalic pathway have been proven in many bacteria including Pseudomonas sp.[154],Bacillus fusiformis [155]. Bacillus thermoleovorans [156]and Geobacillus sp.[157].The phthalic pathway also reported for Pseudomonas sp. [154]and Arthrobacter sp.[158].Therefore information of bacterial degradation of naphthalene has been used to understand and predict pathways in the degradation of three or more ring PAHs [159,160].The proposed pathway of degradation Naphthelene by Pseudomonas sp. CZ2 and CZ5 can be shown in Figure 5[161]. GC/MS analysisby Abo-State et.al.,(2018)[69] revealed that Bordetella avium MAM-P22 degraded Naphthalene to six intermediate compounds, these compounds were 1,2- benzene dicarboxylic acid, Butyl - 2,4- dimethyl -2 - nitro - 4- Pentenoate, 1- Nonen- 3 - ol, Eicosane Nonacosane as indicated in Figure 6 [69].

Phenanthrene degradation pathways

Bacterial degradation of phenanthracene is initiated by 3, 4-dioxygenase to give cis-3, 4- dihydroxy 3,4- dihydrophanthrene, which undergoes enzymatic dehydrogenation to 3,4- dihyroxyphenanthrene)[122,158].

The proposed phenanthrene degradation pathway [162]by managrove enriched bacteria consortium was indicated in Figure 7.This pathway followed the phthalic pathway.

Shingomonas sp. GY2B can degraded Phenanthrrene efficiently as indicated in Figure 8[163],but it is following the salicylate route.

Bacteria can oxidise Phenanthrene to cis- 1, 2-dihydroxy-1, 2-dihydrophenanthrene which converts to 1,2-dihydrophenanthrene when it undergoes enzymatic dehydrogenation. The compounds can be oxidized further to 1-hydroxy-2-naphthoic acid, 2- carboxy benzaldhyde, O-phthalic acid, and proto-catechuic acid as shown in Figure 9 [164].

4-[1-hydroxy (2-naphthyl)-2-oxobut-3enoic acid] which was considered an intermediate product of Phenanthrene biodegradation by Pseudomonas sp. BZ-3.strain BZ-3 initiates its attack on Phenanthrene by deoxygenating at C-3 and C-4 position to produce cis-3, 4 dihydrodiol. Which converted to salicylic acid pathway as indicated in Figure 10 [165].

Phenanthrene degradation by Pseudomonas mendocina revealed that high level accumulation of the (1H2N) was observed[166].The 2-naphthol (decarboxylated product) of 2H1NA was detected as minor metabolite in the degradation of Phenanthrene by Staphylococcus sp. Strain PN/Y[167]. Which was further metabolized by unique meta-cleavage dioxygenase, leading to TCA intermediates [168].

Figure 11 indicated that Phenanthrene is initial transformed to cis-dihydro- diol by PAH dioxygenase (a multi component of dioxygenase enzyme system); dihydrodiol dehydrogenase converts dihydrodiol to caticol and then caticol is degraded into aldehyde or acids by 2, 3 dioxygenase [150],as shown by aerobic bacteria. Pagnot et.al.,(2007 )[169] isolated and characterized the gene cluster involved in Phenanthrene degradation by 3, 4 Phenanthrene dioxygenase and meta-cleavage. A high branched metabolic pathways of Phenanthrene biodegradation by Mycobacterium aromativorans strain JSI9b1T including deoxygenation on C-1,2 and C3,4 and C-9,10 position and ring opening via both ortho- and meta cleavage [170,171].Dimethylphthalate formation proved that Psudomonas sp.USTB-RU degraded phenanthrene via protocatechuate pathway, while Stenotrophomonas maltophilia C6 degraded Phenanthrene via protocatechuate and salicylate pathway [172].

Benzo[a] anthracene degradation pathways:

Initial enzymatic oxidation of aromatic ring system of B-[a]-anthracene may occur at various locations on the molecule, including 1,2 or 3,4-carbon positions, an angular Kata-type initial deoxygenation, via the 9,10- or 10, 11- carbon positions a linear kata-type initial deoxygenation, or via the K-region at 5,6-carbon position as indicated in Figure12.Metabolites from the biotransformation of Benzo[a]anthracene (B[a]A) by bacteria have identified from only six organisms (i) Shingobium yanoikuyae mutant strain B8/36. Initial step of B[a] anthracene was oxidation to produce Benzo[a]anthracene 7, 12 dione, in which further oxidation and ring fission transformed to indo-5-aldhyde and benzene ethanol and number of acids, alchols and esters[173].The two proposed pathways for the parent strain MAM-62 and gamma induced mutant strain MAM-62(4) revealed that the parent and mutant are different in some of their metabolites as summarized in Table 3 and Figures 13, 14 [92].

Pyrene degradation pathways:

Mycobacterium AP1 grew with pyrene as sole carbon and energy source. This strain initiates its attack on pyrene by either monooxygenase or dioxygenase at its C4, C5 positions to give Trans - or cis-4, 5 dihydroxy-4, 5- dihydropyrene. Dehydrogenation of the latter, ortho cleavage of the resulting diol to form phenanthrene 4, 5-dicarboxylic acid and the subsequent decarboxylation to phenanthrene 4-carboxylic acid, the latter with further degradation via phthalate pathway continue to TCA cycle A metabolite (6, 6-dihydroxy-2, 2-biphenyl dicarboxylic acid indicated a new branch in the pathway [174]as indicated in Figure 15.

The major pathways for the metabolism of Phenanthrene and pyrene by another Mycobacterium sp. strain vanbaalenii PYR-1 were initiated by oxidation at the K-regions [174]. Phenanthrene 9, 10 and pyrene-4, 5 di-hydrodiols were metabolized via transient catechol to the ring fission products, 2, 2-diphenic acid and 4, 5-dicarboxyphenanthrene respectively[122].Also another Mycobacterium sp. strain KMS can grow on pyrene. Various key metabolites including pyrene-4, 5-dione, cis-4, 5-pyrene-dihydrol, phenanthrene-4, 5- dicarboxylic acid and 4- Phenanthroic acid [123].The same bacterial strain PYR-1 was able to utilize pyrene as sole carbon and energy source and produces 7 metabolites as indicated in Figure 16. These metabolites including four ring metabolities (mono-hydroxy pyrenes and three different di-hydroxy pyrene) and three-ring metabolites (dihydroxyphenanthrene, 4-phenanthrene-carboxylic acid and 4- phenanthrol), of which more 4- ring metabolites accumulated compared with 3-ring metabolites [175]as indicated in Figure16.

As shown in Figures (17-19), the initial step in pyrene degradation pathway was the oxidation of K region by dioxygenase to form cis-4, 5- pyrene-dihydrol. When 3, 4- di-hydroxy Phenanthrene is formed it enters the Phenanthrene degradation pathway [159,176,177].One of the main metabolites 4-hydroxy-Phenanthrene was transformed into naphthol and 1, 2- dihydroxy- naphthalene which was further degraded through salicylic acid pathway and phatholic acid pathway separately[178].

Abo-State et.al.,(2014)[91] proposed pathways of pyrene degradation by the parent strain Bacillus amyloliquefaciens MAM-62 and its gamma radiation induce[d mutant MAM-62 (4) as summarized in Table 4and Figure 20 revealed that none of the metabolites formed by the mutant strain and also none of the metabolites formed by the mutant have been recorded by the parent Bacillus strain. Pyrene by successive oxidation and ring fission produces benzene ethanol and 2, 4, 6 cycloheptatriene-1-one and acids by the parent strain while it produces butonic acid, 3-methyle 2-phenyl ethyl ester and methyl-2, 3-di-O-acetyl-B-D-xylopyranoside by the mutant MAM-62 (4)[91].

The role of mononuclear iron in dihydroxylation reaction for pyrene have been indicated in Figure 21 [179].In case of pyrene degradation pathway by Pseudomonas stutezeri CECT930, it produces 1-hydroxy-2-naphthoic acid, phthalic acid and cinnamic acid as shown in Figure 22 [180]. Main while, the degradative pyrene proposed pathway by Bacillus altitudinis MAM-8 identified by16 S rRNA reveled the formation of the following metabolites 1-[(hexadeulerio)phenyl] naphthalene; trans-4, 4-di methyoxy -beta methyl chalcone, phthalic acid monocyclohexyl ester, phatholic acid monobutyl ester, dimethoxybenzyl-ide neacetone and phathalic anhydride. Abo-State et.al., (2017) [67] found that,the previous metabolites indicated that pyrene degradation by Bacillus altitudinis MAM-8 followed the phthalic pathway as indicated in Figure 23 [67]. In another study, Abo-State et.al.,(2018a)[68]proposed that pathway of pyrene by the isolated strain from petroleum contaminated soil of Suez Canal, Egypt and identified by16S rRNA as Pseudomonas panipatensis MAM-P39 with accession number MF150314b produced 14 intermediates. These metabolites including 3-methyl penta-1, 4- diene-3-ol; 3-methyl-2-butenoic acid, 3-methyl-but-2-enyl ester; 3 hexanone; 3-methyl-2- butenoic acid, 2-pentyl ester and benzene, (3,3- dimethyl-4- pentyl- as shown in Figure 24 [68].Not only single bacterial isolates or strains were able to degrade pyrene, but also mangrove enriched bacterial consortium. It is well known that consortium having a number of different bacterial collection owing a battery of degradative enzymes more efficient than single bacterial strain. The proposed pathway was indicated in Figure 25 [162].

Benzo [a] Pyrene degradation pathways

Few researches have been conducted on HMW-PAHs especially five fussed rings like benzo [a] pyrene. As it is well known that as the number of fussed rings increased, the ability of bacteria to degrade HMW - PAHs decreased. One of the bacterial sp. (Mycobacterium vanbaalenii PYR-1) was able to degrade Benzo [a] pyrene as indicated in Figure 26[181].However, O-methylation of benzo [a] pyrene as indicated by Zeng et al., (2013)[182] isthe key of the proposed pathway (Figure 27), the degradation was conducted by two steps.

I) removal of 6 - benzo - [a] pyrenyl acetate to form methoxybenzo - [a] pyrene and

II) Transformation of the tree quinones into dimethoxy benzo [a] pyrene.

Treatment of petroleum refinery wastewater (RWP)

Petroleum refinery is an example of an industrial facility which produces a wastewater containing a range of hydrocarbon compounds[183].It also uses a lot of process water [184].This Wastewater released from petroleum refineries is characterized by the presence of large quantity of petroleum products, polycyclic and aromatic hydrocarbons, phenols, metal derivatives, surface active substances, sulfides, naphthylenic acids and other chemicals[185].Wastewaters that containing PAHs must be treated before discharge in water bodies to avoid environmental pollution and comply with environmental protection regulations [186].

Heavy metals together with various pollutants can cause numerous hazards to both human and environment even at low concentration due to gradual accumulation[187].The removal of various toxic substances from wastewater has been a core interest of many researcher [188].

Wastewater may be treated by physiochemical or biological methods, biological treatment is preferred over physicochemical as the former is cost effective, efficient and environmentally friendly [22,189].

Crude oil (C8-C35) was removed by 83.70% by the halotolerant Hydrocarbon Utilizing Bacterial Consortium (HUBC) obtained from on-Shore sites [52].

Consortium of 15 indigenous bacterial isolates removed 94.84% and 93.75% of total Aliphatic and Aromatic Components of Crude Oil (OGDCL, Pakistan) after 24 h respectively [190]. However, the biosurfactant producing Pseudomonas aeruginosa UKMP-14T degraded 75.2% of total petroleum hydrocarbon of tap is crude oil after 7 days at 40oC,and 150 rpm[191].

Using Pseudomonas panipatensis MAM-P39 for treatment of the petroleum refinery wastewater produced from Suez oil processing company degrade 56.28% of organic compounds as determined by GC/MS. Also, this strain can remove 58.92% of Pb, 64.41% of Cd, 67.87% of as and 99.89 of Hg as verified by ICP analysis [192].

Treatment of petroleum refinery wastewater by physicochemical treatment and that treated with Bordetella bronchiseptica MAM-P14 and Bordetella avium MAM-P22 revealed that degradation of 9- methylene-fluorene were 69.6%, 42.0% and 76.9% respectively and degradation of 4-chloro-alfa-naphthol were 73.6%, 74.4% and 49.9%. However, treatment by petroleum refinery wastewater by Bordetella bronchiseptica MAM-P14 removed 58.5%, 84.8% of vanadium and cadmium respectively. While Bordetella avium MAM-P22 removed 71.6% and 82.3% of the same metals [193].

Figure 1: Chemical structures of some PAH compounds.

Figure 2: Proposed pathway for the degradation of naphthalene by Pseudomonas putida [149].

Figure 3: Proposed pathway for the degradation of naphthalene by Streptomyces griseus [150].

Figure 4: Naphthalene biochemical biodegradation pathways. (a) Phthalic pathway (b) Salicylate pathway [151,152]. Discontinuous arrows show molecules identified by Gas Chromatography (GC) analysis.

Figure 5: Proposed pathway for the degradation of naphthalene by strains Pseudomonas sp. CZ2 and CZ5. I, Naphthalene dioxygenase; II, catechol 1, 2-dioxygenase; III, catechol 2, 3-dioxygenase. CZ2, Pseudomonas sp. CZ2; CZ5, Pseudomonas sp. CZ5 [162].

Figure 6: Proposed pathway of Naphthalene by Bordetella avium MAM-P22 [70].

Figure 7: Proposed Phenanthrene degradation pathways by the Managrove enriched bacterial consortium [163].

Figure 8: Proposed pathway for the degradation of Phenanthrene by Sphingomonas sp. [164].

Figure 9: Proposed catabolic pathways of Phenanthrene by aerobic bacteria. The compounds are 1, Phenanthrene; 2, cis -1,2-dihydroxy- 1,2- dihydrophenanthrene; 3, 1,2-dihydroxyphenanthrene; 4, 2-[(E)-2- carboxyvinyl]-1-naphthoic acid; 5, trans-4-(2-hydroxynaph-1-yl)-2- oxobut- 3-enoic acid; 6, 5,6-benzocoumarin; 7, 2-hydroxy-1-naphthoic acid; 8, naphthalene-1,2-dicarboxylic acid; 9, cis-3,4-dihydroxy-3,4- dihydrophenanthrene; 10, 3,4-dihydroxyphenanthrene; 11, 1-[(E)-2- carboxyvinyl]-2-naphthoic acid; 12, trans-4-(1-hydroxynaph-2-yl)-2- oxobut-3-enoic acid; 13, 1-hydroxy-2-naphthoic acid; 14, 7,8- benzocoumarin; 15, 1,2-dihydroxynaphthalene; 16, 2-hydroxy-2H-chromene- 2-carboxylic acid; 17; trans-o-hydroxybenzalpyruvic acid; 18, salicylaldehyde; 19, salyclic acid; 20, trans-2-carboxybenzalpyruvic acid; 21, 2-carboxybenzaldehyde; 22, o-phthalic acid; 23, protocatechuic acid; 24, cis-9,10-dihydroxy-1,2-dihydrophenanthrene; 25, 2,2/- diphenic acid [165].

Figure 10: A proposed pathway for the degradation of Phenanthrene by Pseudomonas sp. BZ-3 [166].

Figure 11: Postulated metabolic pathway of PAH-degradation in aerobic bacteria. Enzymes involved in the degradation of PAHs are oxygenase and dehydrogenase [151]. The initial PAH dioxyganase and catechol 2, 3- dioxygenase are encoded by nahA and nahH, respectively.

Figure 12: Pathways proposed for the biotransformation of Benz[a]anthracene by SphingobiumKK22. Metabolites in brackets were not identified in the culture medium [174].

Figure 13: Proposed pathway of benzo-a- anthracene degradation by B. amyloliquefaciens MAM-62 [93].

Figure 14: Proposed pathway of of benzo-a- anthracene degradation by B. amyloliquefaciens MAM-62(4). 

Figure 15: Schemic pathway proposed for the degradation of Pyrene by Mycobacteruim AP1. The product in brackets has not been isolated. Dotted arrows indicate two or more successive reactions, [175].

Figure 16: Proposed degradation pathways of Pyrene by MycobacteruimA1-PYR. An asterisk indicates that the position of the substitutes was hypothesized. A solid arrow indicates a single reaction and a broken arrow represents two or more transformation steps. COOH -carboxyl group, OH - hydroxyl group, [176].

Figure 17: Proposed pathway for the degradation of pyrene by Mycobacterium sp. strain PYR-1 [160].

Figure 18: Proposed pathway for the degradation of pyrene by Mycobacterium flavescens [177].

Figure 19: Elucidation of Pyrene degradation pathway in Pseudomonas-BP10, [178].

Figure 20: Proposed pathway of of pyrene degradation by B. amyloliquefaciens MAM-62 and MAM-62(4) [92].

Figure 21: A feasible pathway of dihydroxylation reaction catalyzed by R-NDO in strain ustb-1, the Figure displays that the resting R-NDO has a mononuclear iron in ferrous status and an oxidized Rieske [2Fe-2S] center in the active site. At first, one ferric ion in Rieske [2Fe-2S] center is reduced by an external electron from NADH to form a fully reduced R-NDO. Following the binding with the substrate, the dioxygen molecule is activated by the two electrons derived from the mononuclear iron and the reduced Rieske [2Fe-2S] center. Subsequently, the binary complex will quickly react with the carbon–carbon double bond of pyrene at C4-C5 positions to form a Fe-O2-pyrene ternary complex which is a promising intermediate in the formation process of the product. Then a second external electron is used to reduce the ferric ion in the ternary complex. Finally, a proton is introduced to the complex, and then the dihydroxylation product was released. Simultaneously, the mononuclear iron and Rieske [2Fe-2S] center recover the initial states and are ready for the next cycle of the reaction [180].

Figure 22: Proposed metabolic pathway of pyrene by Pseudomonas stutzeri CECT 930 [180].

Figure 23: Proposed metabolic pathway of pyrene by Bacillus altitudinis MAM-P8 [67].

Figure 24: Proposed metabolic pathway of pyrene by Pseudomonas panipatensis MAM-P39 [68] 1 Ethanone,1-(3-buty1-2-hydroxy-5-methylphenyl);2, (1-phenylvinyl) benzene;3, 2,6-di-tert-Butyl-para benzoquinone; 4, Benzene, (3,3-dimethyl-4-pentenyl); 5,2-xylene; 6,isobutyric anhydrid;7 isopropyl (2e)-2-butenoate; 8,3-Hexanone;9, 3- Methylpenta-1,4-diene-3-ol; 10,Farnesol; 11, Octadecanoic acid; 12, 2,6-Dimethyl-8-oxoocta-2,6-dienoic acid, methyl ester; 13, 3-Methyl-2-butenoic acid, 2-pentyl ester; 14, 3-Methyl-2- butenoic acid, 3-methylbut-2-enyl ester.

Table 1: Physical and chemical characters of some PAHs [17,18].

References

1. Varjani JS (2017) Microbial degradation of petroleum hydrocarbons. Bioresour Technol 223: 277-286.
2. Varjani SJ, Upasani VN (2016a) Core flood study for enhanced oil recovery through ex-situ bioaugmentation with thermo- and halo-tolerant rhamnolipid produced by Pseudomonas aeruginosa NCIM 5514. Biores Technol 220: 175-182.
3. Liu B, Xue Z, Zhu X,Jia C (2017) Long-term trends (1990-2014), health risks, and sources of atmospheric polycyclicaromatic hydrocarbons (PAHs) in the U.S. Environ Poll 220: 1171-1179.
4. Margesin R, Schinner F (2001) Biodegradation and bioremediation of hydrocarbons in extreme environments. Appl Microbiol Biotechnol 56: 650-663.
5. Deppe U, Richnow HH, Michaelis W, Antranikian G (2005) Degradation of crude oil by an arctic microbial consortium. Extremophil 9:461- 470.
6. Sajna KV, Sukumaran RK, Gottumukkala LD, Pandey A (2015) Crude oil biodegradation aided by biosurfactants from Pseudozyma NII 08165 or its culture broth. Biores Technol 191: 133-139.
7. Peng RH, Xiong AS, Xue Y, Fu XY, Gao F, et al. (2008) Microbial biodegradation of polyaromatic hydrocarbons. Microbiol Rev 32: 927-955.
8. Li H, Qu R,Li C, Guo W, Han X, et al. (2014) Selective removal of polycyclic aromatic hydrocarbons (PAHs) from soil washing effluents using biochars produced at different pyrolytic temperatures. Biores Technol 163: 193-198.
9. Chen M, Xu P, Zeng G, Yang C, Huang D, et al.(2015) Bioremediation of Soils contaminated with polycyclic aromatic hydrocarbons, petroleum, pesticides, chlorophenols and heavy metals by composting: applications, microbes and future research needs. Biotechnol Adv 33: 745-755
10. Volkering FV, Breure AM, Sterkenburg R, VanAndel JG (1992) Microbial degradation of polycyclic aromatic hydrocarbons effect of substrate availability on bacterial growth kinetics. Appl Microbial Biotech 36: 548-552.
11. Bosma TNP, Middeldorp PJM, Schraa G, Zender AJB (1997) Mass transfer limitation of biotransformation: quantifying bioavailability. Environ Sci Technol 31: 248-252.
12. Masih J, Singhvi R, Kumar K, Jain VK, Taneja A (2012) Seasonal variation and sources of polycyclic aromatic hydrocarbons (PAHs) in indoor and outdoor air in a semiarid tract of Northern India. Aerosol Air Qual Res 12: 515-525.
13. Nouha K, Kumar RS, Tyagi RD (2016) Heavy metals removal from wastewater using extracellular polymeric substances produced by Cloacibacterium normanense in wastewater sludge supplemented with crude glycerol and study of extracellular polymeric substances extraction by different methods. Biores Technol 212: 120-129.
14. Karcher W, Fordham RJ, Dubois JJ, Glaude PGJM, Ligthart JAM (1985) Spectral Atlas of Polycyclic Aromatic Compounds. (Ed.)Dordrecht, D. Reidel Publ. Co, Dordrecht. Boston, Lancaster 13: 227.
15. Utermoehlen CM, Singh M, Lehr RE (1987) Fjord region 3, 4-diol 1, 2-epoxides and other derivatives in the 1, 2, 3, 4- and 5, 6, 7, 8-benzo rings of the carcinogen benzo[g]chrysene. J Org Chem 52: 5574-5582.
16. Lide DR (2005) CRC Handbook of Chemistry and Physics. 86th Ed., Boca Raton, FL, CRC Press2712.
17. Sihag S, Pathak H (2014) A review: Biodegradation of poly aromatic hydrocarbons20. Am J Earth Sci 1: 9-20.
18. Ghosal D, Ghosh S, Dutta T, Ahn Y (2016) Current State of Knowledge in Microbial Degradation of Polycyclic Aromatic Hydrocarbons (PAHs).Front Microbiol 7: 1-26.
19. Masih J, Masih A, Kulshrestha A, Singhvi R, Taneja A (2010) Characteristics of polycyclic aromatic hydrocarbons indoor and outdoor atmosphere in the north central part of India. J Hazard Mater 177: 190-198.
20. IARC [International Agency for Research on Cancer] (2009) Monographs on the evaluation of carcinogenic risks to humans. Complete list of agents evaluated and their classification. France.
21. US EPA (US Environmental Protection Agency) (2007) Technology transfer network. Air toxics web site. Retrieved 29th January 2008.
22. Abdel-Shafy HI, Mansour MSM (2016) A review on polycyclic aromatic hydrocarbons: source, environmental impact, effect on human health and remediation. Egypt J Pet 25: 107-123.
23. Bian L, Zhuqing X, Xianlei Z, hunrong J (2017) Long term trends (1990-2014), health risks, and sources of atmospheric polycyclic aromatic hydrocarbons (PAHs) in the U.S. Environ Poll Environ Poll 220: 1171-1179.
24. Desforges JW, Sonne C, Levin M, Siebert U, Guise SD, et al. (2016) Immunotoxic effects of environmental pollutants in marine mammals. Environ Int 86:126- 139.
25. Jamin EL, Riu A,Douki T,Debrauwer L,CravediJP, et al. (2013) Combined genotoxic effects of a polycyclic aromatic hydrocarbon B(a)P and an heterocyclicamine (PhIP) inrelation to colorectal carcinogenesis. PLOS ONE 3: 58591-58599.
26. Perez-Cadahia B,Lafuente A,Cabaleiro T, Pásaro E, Méndez J, et al. (2007) Initial study on the effects of Prestige oil on human health. Environ Int 33: 176-185.
27. Costa AS, Romao LP, Araujo BR, Lucas SC, Maciel ST, et al. (2012) Environmental strategies to remove volatile aromatic fractions (BTEX) from petroleum industry wastewater using biomass. Biores Technol 105: 31-39.
28. Yu S, Campiglia AD (2005) Direct determination of dibenzo [a, 1] pyrene and its four dibenzopyrene isomers in water samples by solid-liquid extraction and laser-excited time - resolved Shpol’skii spectrometry. Anal Chem 77: 1440-1447.
29. Hecht SS (2002) Human urinary carcinogen metabolites: Biomarkers for investigating tobacco and cancer. Carcinogen 23:907-922.
30. Schvoerer C,Gourier-Frery C,Ledrans M,Germonneau P, Derrien J,et al. (2000) Etude epidemiologique des troubles de sante survenus a` court terme chez les personnes ayant participe au nettoyage des sites pollues par le fuel de ľErika. 5: 57-63.
31. Proctor RN (2001) Tobacco and the global lung cancer epidemic. Nat Rev Cancer 1: 82-86.
32. Perera F, Tang D, Whyatt R, Lederman SA, Jedrychowski W (2005) DNA damage from polycyclic aromatic hydrocarbons measured by benzo[a]pyrene-DNA adducts in mothers and newborns from Northern Manhattan. The World Trade Center Area, Poland, and China. Cancer Epidemiol Biomark Prevent 14: 709-714.
33. Chakravarti D, Venugopal D, Mailander PC, Meza JL, Higginbthms S, et al. (2008) The role of poly cyclic aromatic hydrocarbon DNA adducts in inducing mutations in mouse skin. Mutat Res 649:161-178.
34. IARC [International Agency for Research on Cancer] (2010) Some non-heterocyclic polycyclic aromatic hydrocarbons and some related exposures. In: IARC Monographs on the Evaluation of Carcinogenic Risks to Human. Int Agen Res Cancer, Lyon.France. Monogr Eval Carcinog Risks Hum 92: 765-771.
35. Burnett RT, Thun MJ, Calle EE, Krewski D, Ito K, et al.(2002) Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air poll. JAMA 287: 1132-1141.
36. Lewtas J (2007) Air pollution combustion emissions: Characterization of causative agents and mechanisms associated with cancer, reproductive and cardiovascular effects. Mutat Res 636: 95 - 133.
37. Lee HL, Hsieh DPH, Li LA (2011) Polycyclic aromatic hydrocarbons in cigarette side stream smoke particulates from a Taiwanese brand and their carcinogenic relevance. Chemosph 82: 477-482.
38. Andersson K, Bakke JV, Bjorseth O, Bornehag CG, Clausen G, et al. (1997) TVOC and health in nonindustrial indoor environments - report from a Nordic scientific consensus meeting at langholmen in Stockholm. Int J IndoorAir Air Qual Climate 7: 78-91.
39. Shadi A, Mazandarani MK, Nikpour Y (2012) Concentrations of polycyclic aromatic hydrocarbons (PAHS) in sediments of Khowre-Musa System (Persian Gulf). World 4: 83-86.
40. Crépeaux G, Bouillaud-Kremarik P, Sikhayeva N, Rychen G, Soulimani R, et al.(2013) Exclusive prenatalexposure to a 16 PAH mixture does not impact anxiety-related-related behaviours and regional brain metabolism in adult male rats: Arole for the period of exposure in the modulation of PAH neurotoxicity. Toxicolo Let 221: 40-46.
41. Perera F, Herbstman J (2011) Prenatal environmental exposures, epigenetics, and disease. Reprod Toxicol 31: 363-373.
42. Jyothi PS, Lakshmi MVVC, Harisha KG (2014) A review on poly cyclic aromatic hydrocarbons determination sources, effects and biodegration. Int J Recent Sci Res 5: 415-424.
43. Perera FP, Tang D, Wang S, Vishnevetsky J, Zhang B, et al. (2012) Prenatal polycyclicaromatic hydrocarbon (PAH) exposure and child behavior at age6-7 years. Environ Health Perspect 120: 921-926.
44. ATSDR (2012) Agency for Toxic Substances and Disease Registry, Case Studies in Environmental Medicine Toxicity of Polycyclic Aromatic Hydrocarbons (PAHs) Course: A report 1-68.
45. Becher G, Bjorseth A (1983) Determination of exposure to polycyclic aromatic hydrocarbons by analysis of human urine. Cancer Lett 17:301-311.
46. Granella M, Clonfero E (1993) Urinary excretion of 1-pyrenol in automotive repair workers. Arch. Occup. Environ. Health 65: 241-245.
47. Santella RM, Hemminki K, Tang DL, Paik M, Ottman R, et al. (1993) Polycyclic aromatic hydrocarbon-DNA adducts in white blood cells and urinary 1-hydroxypyrene in foundry workers. Cancer Epidemiol. Biomar Prev 2: 59-62.
48. Popp W (1997) DNA single strand breakage, DNA adducts, and sister chromatid exchange in lymphocytes and phenanthrene and pyrene metabolites in urine of coke oven workers. Occup Environ Med 54: 176-183.
49. CDC (2005) Centers for Disease Control and Prevention. Third National Report on Human Exposure to Environmental Chemicals. Atlanta GA Available from: http://www.cdc.gov/ Exposure Report/pdf/third report.
50. Chaudhry Q, Blom-Zandstra M, Gupta S, Joner EJ (2005) Utilizing the synergy between plants and rhizosphere microorganisms to enhance breakdown of organic pollutants in the environment. Environ Sci Poll Res 12: 34-48.
51. Farhadian M, Vachelard C, Duchez D, Larroche C (2008) In situ bioremediation of monoaromatic pollutants in groundwater: A review. Biores Technol 9: 5296-5308.
52. Varjani SJ, Srivastava VK (2015) Green technology and sustainable development of environment. Renew Res J 3: 244-249.
53. Varjani SJ, Upasani VN (2012) Characterization of hydrocarbon utilizing Pseudomonas Strains from crude oil contaminated samples. Int J.Sci Comput 6: 120-127.
54. Chandra S, Sharma R, Singh K, Sharma A (2013) Application of bioremediation technology in the environment contaminated with petroleum hydrocarbon. Ann Microbiol 63: n417-431.
55. Tiburtius ER, Peralta-Zamora P, Emmel A (2005) Treatment of gasoline-contaminated waters by advanced oxidation processes. J Hazar Mater 126: 86-
56. Mascolo G, Ciannarella R, Balest L, Lopez A (2008) Effectiveness of UV-based advanced oxidation processes for the remediation of hydrocarbon pollution in the groundwater: A laboratory investigation. J Hazard Mater 152: 1138-1145.
57. Singh OV, Jain RK (2003) Phytoremediation of toxic aromatic pollutants from soil. Microbiol. Biotechnol. 63: 128-135.
58. Vidali M (2001) Bioremediation: An overview. Pure Appl Chem 73: 1163-1172.
59. Lynch JM, Moffat AJ (2005) Bioremediation: Prospects for the future application of innovative applied biological research. Ann Appl Biol 146: 217-
60. Wallace S, Kadlec R (2005) BTEX degradation in a cold-climate wetland system. Water Sci Technol 51: 165 - 171.
61. Farhadian M, Larroche C, Borghei M, Troquet J,Vachelard C (2006) Bioremediation of BTEX-contaminated groundwater through bioreactors. 4 ème Colloque Franco-Roumain de chimie appliquée, Université Blaise Pascal, Clermont-Ferrand, France, 28 Juin- 2 Juillet 2006; 438.
62. Varjani SJ, Rana DP, Jain AK, Bateja S, Upasani VN (2015) Synergistic ex-situ biodegradation of crude oil byhalotolerant bacterial consortium of indigenous strains isolatedfrom on shore sites of Gujarat, Int. Biodeter Biodegrad 103: 116-124.
63. Varjani SJ, Upasani VN (2016b) Carbon spectrum utilization by an indigenous strain of Pseudomonas NCIM 5514: production Characterization and surface active properties of bio surfactant. Biores Technol 221: 510 -516.
64. Varjani SJ, Upasani VN (2016c) Biodegradation of petroleum hydrocarbons by oleophilic strain of Pseudomonas aeruginosa NCIM 5514. Biores Technol 222: 195-201.
65. Abbasian F, Lockington R, Mallavarapu M, Naidu R (2015) A comprehensive review of aliphatic hydrocarbon biodegradation by bacteria. Appl Biochem Biotechnol 15: 1603-1605.
66. Meckenstock RU, Boll M, Mouttaki H, Koelschbach JS, Tarouco PC, et al. (2016) Anaerobic degradation of benzene and polycyclic aromatic hydrocarbons. J Mol Microbiol Biotechnol26: 92-118
67. Abo-State MAM, Abdallah N, Nader B (2017) Biodegradation of high molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) mixtures by bacteria isolated from soils polluted with petroleum oil. 1st International Conference on Biological and Environmental Science and Application (ICBESA) 23 -25 March 2017 Luxor, Egypt.
68. Abo-StateMAM, EL- Dars FMS, Abdin BA (2018 a) Isolation and identification of Pyrene degrading bacterial and its pathway from Suez Oil Processing Company, Suez , Egypt. J Ecol Health Environ 6: 63 -76.
69. Abo-Stat, MAM, Riad BY, Abdel Aziz MF (2018 b) Biodegradation of naphthalene by Bordetella avium isolated from Petroleum refinery wastewater in Eygept and its pathway. J Rad Res Appl Sci 11: 1-9.
70. Semple KT, Reid BJ, Fermor TR (2001) Impact of composting strategies on the treatment of soils contaminated with organic pollutants. Environ Pollut 112: 269- 283.
71. Harayama S (1997) Polycyclic aromatic hydrocarbon bioremediation design. Curr Opin Biotech 8:268-273.
72. Müncnerová D, Agustin J (1994) Fungal metabolism and detoxification of polycyclic aromatic hydrocarbons: A review. Bioresour Technol 48: 97-106.
73. Lioyd-Jones G, Hunter DWF (1997) Characterization of fluoranthene and pyrene-degrading Mycobacterium-like strains by RAPD and SSU sequencing. FEMS Microbiol Lett 153: 51-56.
74. Samanta SK, Bhushan B, Jain RK (2001) Efficiency of naphthalene and salicylate degradation by a recombinant Pseudomonas putida mutant strain defective in glucose metabolism. Appl Microbiol Biotech 55: 627-631.
75. Aitken MD, Stringfellow WT, Nagel RD, Kazunga C, Chen SH (1998) Characteristics of phenanthrene-degrading bacteria isolated from soils contaminated with polycyclic aromatic hydrocarbons. J Can Microbiol 44: 743-752.
76. Baldwin BR, Mesarch MB, Nies L (2000) Broad substrate specificity of naphthalene and biphenyl-utilizing bacteria. Appl Microbiol Biotech 53: 748-753.
77. Barathi S, Vasudevan N (2001) Utilization of petroleum hydrocarbons by Pseudomonas fluorescens isolated from a petroleum -contaminated soil. Environ Int 26: 413-416.
78. Cheung PY, Kinkle BK (2001) Mycobacterium diversity and pyrene mineralization in petroleum contaminated soils. Appl Environ Microbiol 67: 2222-2229.
79. Abdelhaleem HAR, Zein HS, Abdel Aziz A, Sharaf AN, Abdel Hadi AA (2019) Identification and characterization of novel bacterial polyaromatic hydrocarbon-degrading enzymes as potential tools for cleaning up hydrocarbon pollutents from different environmental sources. Environ Toxicol Pharm 67: 108-116.
80. Maeda AH, Nishi S, Ozeki Y, OhtaY, Hatada Y, et al. (2013) Draft genome sequence of Sphingobium starin kk22, a high-molecular-weight polycyclic aromatic hydrocarbon-degrading bacterium isolated from cattle pasture. Genome Announ 1: 1-2.
81. Mclellan SI, Warshawsky D, Shann JR (2002) The effect of polycyclic aromatic hydrocarbons on degredation of ben 30 (a) pyrene by Mycobacterium Starin RJG 2-135. Environ Toxicot Chem 21: 253-259.
82. Kim S,Kweon O, Freeman JP, Jones RC, Adjei MD, et al. (2006) Molecular cloning and expression of genes encoding a novel dioxygenaseinvolved in low-andhigh molecular-weight polycyclic aromatic hydrocarbon degradation in Mycobacterium vanbaalenii PYR-1. Environ Microbiol 72: 1045-1054.
83. Hunter RD, Ekunwe SIN, Dodor DE, Hwang HM, Ekunwe L (2005) Bacillus subtilis a potential degrader of pytene and Benzo[a]pyrene. Int J Environ Res Public Health 2: 267- 271.
84. Dan S, Pei-Jun L, Stagnitt F, Xian-Zhe X (2006) Biodegradation of Ben 30 (a) pyrene in soil By Mucor sp SF06 and Bacillus SB02 co immobilized on vermiculite. J Environ Sci 18: 1204 -1209.
85. Das K, Mukherjee AK(2007) Differential utilization of pyrene as the sole source of Crbon byBacillussubtilisand Pseudomonas aeruginosa strains: Role of biosurfactants in enhancing bioavailability. J Appl Microbiol 102: 195 - 203.
86. Khanna P, Goyal. D, Khanna.P (2012) Characterization of pyrene utilizing Bacillus from crude oil contaminated soil. Braz J Microbiol 43: 606-617.
87. Maiti A, Das S, Bhattacharyya N (2012) Bioremedation of high molecular weight polycuclic aromatic hydrocarbons by Bacillus thuringiensis strain NA2. J sci 1: 72- 75.
88. Syakti AD, Yani M, Hidayati NV, Siregar AS, Doumenq P, et al. (2013) The bioremediation potential of hydrocarbon classier bacteria isolated from a mangrove contaminated by petroleum hydrocarbons on the cilacap coast Indonesia. Bioremed J 17: 11-20.
89. Liu S, Hou Y, Sun G (2013) Synergistic degradation of pyrene and volatilization of arsenio by coo cultures of bacteria and a fungus. Front Environ Sci Eng 7: 191-199.
90. Abo-State MAM ,Saleh Y, Partila A (2013) Identification of Polycyclic aromatic hydrocarbon degrading bacterial strain and its ability to degrade pyrene. J World Appl Sci 23: 515 -525.
91. Abo-State MAM, Saleh YE, Partila AM (2014) Identification of polycyclic aromatic hydrocarbon degrading bacterial strain and its ability to degrade pyrene. Firest Middle East Molucular Biology Congress (MEMBS), Dubai, UAE, 14-17 Sept.
92. Abo-State MAM, Saleh Y, Partila A (2015) Studying the ability of polycyclic aromatic hydrocarbon degrading bacterial strain to degrade Benz[a]anthracene and its pathway. Second Middle East Molecular Biology Congress (MEMBC), Istanbul, Turkey.17-20, September, 2015.
93. Jorfi S, Rezaee A, Mobeh-Ali GA, Jaafarzadeh NA (2013) Application of Biosurfactants produced by Pseudomonas aeruginosa SP4 for Bioremediation of soils Contaminated by Pyrene. Soil Sedim Contamin 22: 890-911.
94. Feng T, Lin H, Tang, J, Feng Y (2014) Characterization of polycyclic aromatic hydrocarbons degradation and arsenate reduction by aversatile pseudomonas Inter Biodeter Biodegrad 90: 79-87.
95. Chaudhary P, Sahay H,Sharma R,pandey AK, Singh SB, et al. (2015) Identification and analysis of polyaromatic hydrocarbons (PAHS)-biodegrading bacterial strains from refinery soil of India. Environ Monit Assess 187: 1-9.
96. Singh A, kumar K, Pandey AK, Sharma A, Singh SB, et al. (2015) Pyrene degradation by biosurfactantproducing bacterium Stenotriohomonas maltophilia. Agric Res 4: 42-47.
97. Adebusoye SA, Okpalanozie O, Nweke NC (2015) Isolation and characterization of bacterial strains with pyrene metabolic functions from cow dung and Terminalia catappa Biocatal.Agricultur Biotechnol 4: 778-783.
98. Akinbankole AS, Tunung R, Tennant AM (2015) Biochemical and Molecular characterization of pyrene and anthracene metabolizing bacteria isolated from oil contaminated water and soil in Malaysia. J Appl Environ Microbial 25 -30.
99. Dave BP, Ghevariya CM, Bhatt JK, Dudhagara DR, Rajpara RK (2014) Enhanced biodegradation of total polycyclic aromatic hydrocarbons (TPAHs) by marine halotolerant Achromobacter xylosoxidans using Triton X- 100 and b-cyclodextrin-A microcosm approach. Marine Pollut Bull 123-129.
100. Badejo AC, Choi CW, Badejo AO, Shin KH, Hyun JH, et al. (2013) global proteome studyof Mycobacterium gilvum PYRGCK grown on pyrene and glucose reveals the activation of glyoxylate, shikimate and gluconeogenetic pathways through the central carbon metabolism highway. Biodegrad 24: 741- 752.
101. Fu B, Li QX, Xu T, Cui ZL, Sun Y, et al. (2014) Sphingobium sp.FB3 degrades a mixture of polycyclic aromatic hydrocarbons. Int Biodegrad 87: 44-51.
102. Valsala H, Prakash P, Elavarasi V, Pugazhendhi A, Thamaraiselvi K (2014) Isolation of Staphylococcus mepalensis for degradation of pyrene from diesel contaminated site. Inter J Comp Appl 0975-8887: 21-24.
103. Isaac P, Martinez FL, Bourguignnon N, Sanchezz LA, Ferrero MA (2015)Improved PAHs removal performance by a defined bacterial consortium of indigenous Pseudomonas and Actinobacteria from Patagonia, Argentina. Int Biodetorio Biodegrad 101: 23-31.
104. Bourguignon N, Isaac P, Alvarez H, Amoroso MJ, Ferrero MA (2014) Enhanced polyaromatic hydrocarbon degradation by adapted cultures of actinomycete strains. J Basic Microbiol 54: 1288 -1294.
105. Ma J, Xu L, Jia L (2013) Characterization of Pyrene degradation by Pseudomonas Strain Jpyr-1isolated from active sewage sludge. Biores Technol 140: 15-21.
106. Sun k, Liu J, Jin L, Gao Y (2014) Utilizing Pyrene degrading endophytic bacteria to reduce The Risk of plant pyrene contamination. Plant Soil 374: 251-262.
107. Sharma T (2014) In silico investigation of polycyclic aromatic hydrocarbons against bacterial 1-2 dioxygenase. J Chem Pharm Res 6: 873-877.
108. Kuppusamy S, Thavamani P, Megharaj M, Naidu R (2016) Biodegradation 546 of polycyclic aromatic hydrocarbons (PAHs) by novel bacterial consortia tolerant 547 to diverse physical settings: Assessments in liquid- and slurry-phase systems. Int Biodeter Biodegrad 108: 149-157.
109. Al- Thukair AA, malik k (2016) Pyrene metabolism by the novel bacterial strains Burkholderia fungorum T3A13001 and caulobacter sp (T2A12002) isolated from an oil - polluted site in Arabian gulf gnt . Biodeter Biodegrad 110: 32-37.
110. Zhao F, Zhou JD, Ma F, Shi RJ, Han SQ, et al. (2016) Simultaneous inhibition of sulfate-reducing bacteria, removal of H2S and production of rhamnolipid by recombinant Pseudomonas stutzeri Rhl: Applications for microbial enhanced oil recovery. Biores Technol 207: 24-30.
111. Sowada J, Schmalenberger A, Ebner I, Luch A, Tralau T (2014) Degradation of benzo [a] pyrene by bactedruak isolates from human skin. FEMS Microbiol Ecol 88: 129-139.
112. Lily MK, Bahugua A, Dangwal K, Garg V (2010) Optimization of an inducible, Chromosomally encoded benzo [a] pyrene (BaP) degradation pathway Bacillus subtilis BMT4i (MTCC9447). AnnMicrobio 60: 51-58.
113. Lily MK, Bahuguna A, Bhatt KK, Garg V,Dangwal k (2012) Strain improvement of a Potent benzo[a] pyrene (BAP) degrader Bacillus Subtilis BMT4I (MTXX 9447). Intern J Adv Biotechnol Res 3: 570-577.
114. Okai M,Kihara L, Yokoyama Y, Ishida M,Urano N (2015) Isolation and characterization of benzo [a] pyrene-degrading bacteria from the Tokyoo Bay area and Tama River in Japan. FEMSMicrobiol362: 1-7.
115. Folwell BD, Mc Genity TJ, Whitby C (2016) Biofilm and planktonic bacterial and communities transforming hight- Molecular weight polycyclic aromatic hydrocarbons. Appl Environ Microbiol 82:2288- 2299.
116. Das N, Chandran P (2011) Microbial degradation of petroleum hydrocarbon contaminants: An overview. Biotechnol Res Int 2011: 1-13.
117. Karigar CS, Rao SS (2011) Role of Microbial Enzymes in the Bioremediation of Pollutants. Enzyme Res 1: 1-11.
118. Arora PK, Kumar M, Chauhan A, Raghava GP, Jain RK (2009) OxDBase: a database of oxygenases involved in biodegradation. Bio Med Cent Res Notes 2: 1-9.
119. Gao C, Hu C, Ma C, Su F, Yu H, et al. (2012) Genome sequence of theLactate-utilizing Pseudomonas aeruginosa strain XMG. J Bacteriol 194: 4751- 4752.
120. Lalucat JA, Bennasar R, Bosch E, García-Valdés, Palleroni NJ (2006) Biology of Pseudomonas stutzeri. Mol Biol Rev 70: 510-547.
121. Kim SJ, Jones RC, Cha CJ, Kweon O, Edmondson RD, et al. (2004) Identification of proteins induced by polycyclic aromatic hydrocarbon in Mycobacterium vanbaalenii PYR-1 using two-dimensional polyacrylamide gel electrophoresis and de novo sequencing methods. Proteomics 4: 3899-3908.
122. Kim YH, Freeman JP (2005) Effects of pH on the degradation of phenanthrene and pyrene by Mycobacterium vanbaaleniiv PYR-1. Appl Microbiol. Biotechnol 67: 275-285.
123. Liang Y, Gardner DR, Miller CD, Chen D, Anderson AJ,et al. (2006) Study of biochemical pathways and enzymes involved in pyrene degradation by Mycovaterium StrainKMS. Appl Environ Microbiol 72: 7821-7828.
124. Lee SE, Seo JS,Keum YS, Lee KJ, Li QX (2007) Fluoranthene metabolism and associated proteins in Mycobacterium JS14. Proteomics 7: 2059-2069.
125. Buckova M, Puskarova A,Chovanova K, Krakova L, Feriance P, et al.(2013) A simple strategy for investigating the dversity and hydrocarbon degradation abilities of cultivable bacteria from contaminated soil. World J Microbiol Biotechnol 29: 1085 - 1098.
126. Wongwongsee W, Charean pat P, pinkakong O (2013) Abilities and genes for PAH biodegradation of Bactria isolated from mangrove sediments from central of Thailand marine. Poll Bull 74: 95-104.
127. Lyu Y, Zheng W, Zheng T, Tian Y (2014) Biodegradation of Polycyckuc Aromatic Hydrocarbons by Novosphingobium pentaromativorans US6-1. PLOS ONE 9: 1-8.
128. Yun SH, Choi CW, Lee SY,Lee YG, Kwon J,et al.(2014) propteomic characterization of plasmid pLA1 for biodegeneration of Polycyclic Aromatic Hydrocabons in the marine bacterium, Novosphingobium pentaromativorans US6-1. PLOS ONE 9: E90812.
129. Sawulski P, Clipson N, Doyle E (2014) Effects of polycyclic aromatic hydrocarbons on microbial community structure and PAH ring hydroxylating dioxygenase gene abundance in soil. Biodegrad 25: 835-847.
130. Kweon O, Kim SJ, Kim DW, Kim JM, Kim HL, et al. (2014) Pleiotropic and epistatic behavior of a ring-hydroxulating oxygenase system in The polycyclic aromatic hydrocarbon metabolic network from Mycobacterium vanbaalenii PYR-1. J Bacterial196: 3503-3515.
131. Muangechinda C, Chavanich S, Viykarn V, Watanabe K, Imura S, et al. (2015) Abundance and diversityof functional genes involved in thedegradation ofaromatic hydrocarbonin Antharctic soils and sedements around Syowa station. Environ Sci Poll Res 22: 4725-4735.
132. Darmawan R, Nakata H, Ohta H, Niidome T, Takikawa K, et al. (2015) Isolation and Evaluation of PAH degrading bacteria. J Bioremed Biodeg 6: 2-7.
133. Li F, Zhu L, Wang L, Zhan Y (2015) Gene expression of an Arthrobacter in surfactant-enhanced biodegradation of a hydrophobic organic compound.Environ. Sci Technol 49: 3698-3704.
134. Liang C, Huang Y, Wang H (2019a) Pah E a functionnnnal marker gene for polycyclic aromatic hydrocarbon-degrading bacteria. Appl Environ Microbiol.
135. Liang C, Huang Y, Wang Y, Ye Q, Zhang Z, et al. (2019b) Distribution of bacterial polycyclic aromatic hydrocarbon ( PAH) ring-hydroxylating dioxygenases genes in oil field soils and mangr-ove sediments, explored by gene- targeted metagenomics. Appl Microbial Biotechnol 103: 2427- 2440.
136. Déziel E, Paquette G, Villemur R, Lépine F, Bisaillon JG (1996) Biosurfactant production by a soil Pseudomonas strain growing on polycyclic aromatic hydrocarbons. Appl Environ Microbiol 62: 1908-1912.
137. Abo-State MAM, Mostafa YH (2005) Biodegradation of polycyclic aromatic hydrocarbons from two petroleum crude oils Egypt. J Biotechnol 20: 367-384.
138. Saleh YE, Abo-State MAM, Aziz N, Partila AM (2013) Isolation of polycyclic aromatic hydrocarbon degrading bacterial strains isolated from indigenous microbial communities of petroleum contaminated soils. World Appl Sci J 23: 554-564.
139. Varjani SJ, Rana DP, Jain AK, Bateja S, Upasani VN (2015) Synergistic ex-situ biodegradation of crude oil by halotolerant bacterial consortium of indigenous strains isolatedfrom on shore sites of Gujarat, India. Int Biodeterior Biodegradation 103: 116-124.
140. Hendrickx B, Junca H, Vosahlova J, Lindner A, Ruegg I, et al. (2006) Alternative primer sets for PCR detection of genotypes involved in bacterial aerobic BTEX degrading isolates and in subsurface soils of BTEX-contaminated industrial site. J Microbiol Methods 64: 250-256.
141. Hendrickx B, Junca H, Vosahlova J, Lindner A, Ruegg I, et al. (2014) Flavin dependent monooxygenases. Arch Biochem Biophys 544: 2-17.
142. Kanaly RA, Harayama S (2000) Biodegradation of high-molecular-weight polycyclic aromatic hydrocarbons by bacteria. J Bacteriol 182: 2059-2067.
143. Zhang Z, Hou Z, Yang C, Ma C, Tao F, et al. (2011) Degradation of n-alkanes and polycyclic aromatic hydrocarbons in petroleum by a newly isolated Pseudomonas aeruginosa Biores Technol 102: 4111-4116.
144. Peng RH, Xiong AS, Xue Y, Fu XY, Gao F, et al.(2008) Microbial biodegradation of polyaromatic hydrocarbons. FEMS Microbiol Rev 32: 927-955.
145. Jaekel U, Musat N, Adam B, Kuypers M , Grundmann O, et al. (2013) Anaerobic degradation of propane and butane by sulfate-reducing bacteria enriched from marine hydrocarbon cold seeps. ISME J 7: 885-895.
146. Wilkes H, Buckel W, Golding BT, Rabus R (2016) Metabolism of hydrocarbons in n-Alkane utilizing anaerobic bacteria. J Mol Microbiol Biotechnol 26: 138 - 151.
147. Rockne KJ, and Strand SE (2001) Anaerobic biodegradation of naphthalene, Phenanthrene and biphenyl by a denitrifying enrichment culture. Water Res 35: 291-299.
148. Reshetilov AN, Iliasov PV, Filonov AE, Gayazov RR, Kosheleva IA, et al. (1997) Pseudomonas putida as a receptor element of microbial sensor for naphthalene detection. Proc Biochem 32: 487-493.
149. Gopishetty SR, Heinemann J, Deshpande M, and Rosazza JPN (2007) Aromatic oxidations by Streptomyces griseus: Biotransformations of naphthalene to 4-hydroxy-1-tetralone. Enz Microbiol Tech 40: 1622- 1626.
150. Haritash AK. and Kaushik CP (2009) Biodegradation aspects of Polycyclic Aromatic Hydrocarbons (PAHs): A review. J hazard Mate 169: 1-15.
151. Seo JS, Keum YS, Li QX (2009) Bacterial degradation of aromatic compounds. Intern J Environ Res Public Health 6: 278-309.
152. Fernandez M, Niqui-Arroyo JL, Conde S, Ramos JL, Duque E (2012) Enhanced tolerance to naphthalene and enhanced rhizoremediation performance for Pseudomonas putida KT2440 via the NAH7 catabolic plasmid. Appl Environ Microbiol 78: 5104-5110.
153. Izmalkova TY, Sazonova OI, Nagornih MO, Sokolov SL, Kosheleva IA, et al. (2013) The organization of naphthalene degradation genes inPseudomonas putida strain AK5. Res Microbiol 164: 244-253.
154. Jia Y, Yin H, Ye JS, Peng H, He BY, et al. (2008) Characteristics and pathway of naphthalene degradation by Pseudomonas sp N7. Huan Jing Ke Xue 29: 756-762.
155. Lin C, Gan L, Chen ZL (2010) Biodegradation of naphthalene by strain Bacillus fusiformis (BFN). J Haz Mater 182: 771-777.
156. Annweiler E, Richnow HH, Antranikian G, Hebenbrock S, Garms C, et al. (2000) Naphthalene degradation and incorporation of naphthalene-derived carbon into biomass by the thermophile Bacillus thermoleovorans. Appl Environ Microbiol 66: 518-523.
157. Bubinas A, Giedraitytė G, Kalėdienė L, Nivinskiene O, Butkiene R (2008) Degradation of naphthalene by thermophilic bacteria via a pathway through protocatechuic acid. J Cent Eur Biol 3: 61-68.
158. Seo JS, Keum YS, Hu Y, Lee SE, Li QX (2006) Phenanthrene degradation in Arthrobacter P1-1: initial 1, 2-, 3, 4- and 9, 10-dioxygenation and meta- and ortho-cleavages of naphthalene-1,2-diol after its formation from naphthalene-1,2-dicarboxylic acid and hydroxyl naphthoic acids. Chemosph 65: 2388-2394.
159. Cerniglia CE (1992) Biodegradation of polycyclic aromatic hydrocarbons. Biodegrad 3: 351-368.
160. Kim TJ, Lee EY, Kim YJ. Cho KS, Ryu Hw (2003) Degradation of polyaromatic hydrocarbons by Burkholderia cepacia 2A-12. World J Microbiol Biotechnol 19: 411-417.
161. Zhou W, He D, Li X, Zhang H, Zeng X, et al. (2013) Isolation and characterization of naphthalene degrading strains, Pseudomonas CZ2 and CZ .Afr J Microbiol Res 7:13-19.
162. Luan TG, Yu KSH, Zhong Y, Zhou HW, Lan CY (2006) Study of metabolities from the degradation of polycyclic aromatic hydrocarbons (PAHs) by bacterial consortium enriched from mangrove sediments. Chemosph 65: 2289-2296.
163. Tao XQ, Lu GN, Dang Z, Yang C, Yi XY (2007) A phenanthrene -degrading strain Sphengomonas sp GY2B isolated from contaminated soils. Proc Biochem 42: 401-408.
164. Ri-He P, Ai-Sheng X, Yong X, Xiao-Yu F, Feng G, et al. (2008) Microbial biodegradation of polyaromatics hydrocarbons. Shanghai key laboratory of agricultural genetics and breeding agro-biotechnology research institute, shanghai academy of agricultural sciences, and shanghai China. FEMS Microbiol Rev 32: 927-955.
165. Zeinali M, Vossoughi M, Ardestani SK (2008) Degradation of phenanthrene and anthracene by Nocardia otitidiscaviaru strain TSH1, a moderately thermophilic bacterium. J Appl Microbiol 105: 398-406.
166. Tian L, Ma P, Zhong J-J (2002) Kinetics and key enzyme activeties of phenanthrene degradation by Pseudomonas mendocina. Proc Biochem 37: 1431-1437.
167. Mallick S, Chatterjee S, Dutta TK, (2007) A novel degradation pathway in the assimilation of phenanthrene by Staphylococcus strain PN/Y via meta-cleavage of 2-hydroxy-1-naphthoic acid: Formation of trans-2, 3-dioxo-5-(2’-hydroxyphenyl)-pent-4-enoic acid. Microbiol 153: 2104-2115.
168. Mallick S, Dutta TK (2008) Kinetics of phenanthrene degradation by Staphylococcus strain PN/Y involving 2-hydroxy-1-naphthoic acid in a novel metabolic pathway. Proc Biochem 43:1004-1008.
169. Pagnout C, Frache G, Poupin P, Maunit B, Muller JF, et al. (2007) Isolation and characterization of a gen cluster involved in PAH degradation in Mycobacterium strain SNP11: Expression in Mycobacterium smegmatis mc2155. Res Microbiol 158: 175-186.
170. Seo JS, Keum YS, Li QX (2012) Mycobacterium aromativoransJS19b1T degrades phenanthrene through C-1, 2, C-3, 4 and C-9, 10 dioxygenation pathways. Int Biodeterior. Biodegrad 70: 96 -103.
171. Gao S, Seo JS, Wang J, Keum YS, Li J, et al. (2013) Multiple degradation pathways of phenanthrene by Stenotrophomonas maltophilia Int Biodeter Biodegrad 79: 98-104.
172. Masakorala K,Yao J, Cai M, Chandankere R, Yuan H, et al.(2013) Isolation and characterization of a novel phenanthrene (PHE) degrading strain Psuedomonas USTB-RU from petroleum contaminated soil. J Hazard Mater 263: 493-500.
173. Kunihiro M, Ozeki Y, Nogi Y, Hamamura N, Kanaly RA (2013) Benaz [a] anthracene biotransformation and production of ring fission products by Sphingobium strain KK22. Appl Environ Mocrobiol 79: 4410-4420.
174. Vila J, Lipez Z, Sabate J, Minguillon C, Solanas AM, et al. (2001) Identification ofanovel metabolite in the degration of pyrene by Mycobactrium sp. strain AP1: actions of the isolate on two and three-ring polycyclic aromatic hydrocarbons. Appl Environ Microbiol 67: 5497-5505.
175. Zhong y, Luan T, Zhou H, Lan C, Tam NFY (2006) Metabolite production in degradation of pyrene alone or in a mixture with another pplycyclic aromatic hydrocarbon by Mycobacterium Environ Toxicol Chem 25: 2853 -2859.
176. Dean-Ross D, Cerniglia CE (1996) Degradation of pyrene by Mycobacterium flavescens. Appl Microbiol Biotechnol 46:307 -312.
177. Kumari B, Singh SN, Deeba F, Sharma M, Pandey V, et al. (2013) Elucidation of Pyrene degradation pathway in bacteria. Adv Biores 4: 151-160.
178. Ye J, yin H, peng H, Bai J,li Y (2014) Pyrene removal and transformation by Joint application of alfalfa and exogenous microorganisms and their influence on soil microbial community. Ecoloxicol Environ Safty 110:129-135.
179. Jin JN, Yao J, Zhang QY, Yu C, Chen P, et al. (2015) An integrated approach of bioassay and molecular docking to study the dihydroxylation mechanism of pyrene by naphthalene dioxygenase in Rhodococcus sp ustb-1. Chemosphere 128: 307 - 313.
180. Moscoso F, Deive FJ, Longo MA, Sanromán MA (2015) Insights into polyaromatic hydrocarbon biodegradation byPseudomonas stutzeriCECT 930: operation at bioreactor scaleand metabolic pathways. Int J Environ Sci Technol 12: 1243-1252.
181. Moody JD, Freeman JP, Fu PP, Cermiglia CE (2004) Degradation of benzo[a]pyrene by Mycobacterium vanbaalenii PYR-1. Appl Environ Microbiol 70: 340 -345.
182. Zeng J, Lin X, Zhang J, Zhu H, Chen H, et al. (2013) Successive transformation of benzo[a]pyrene by laccase of Trametes versicolor and pyrene degrading Mycobacterium Appl Microbiol Biotechnol 97: 3183 - 3194.
183. Wake H (2005) Oil refineries a review of their ecological impacts on the aquatic environment. Est Coast Shelf Sci 62: 131-140.
184. Lu M, Gu LP, Xu WH (2013) Treatment of petroleum refinery wastewater using a sequential anaerobic-aerobic moving-bed biofilm reactor system based on suspended ceramsite. Water sci Technol 67: 1976- 1983.
185. Musa NM, Abdulsalam S, Suleiman ADI, Abdullahi S (2015) Bioremediation of petroleum refinery wastewater effluent via augmented native microbes.JETEAS 6: 1- 6.
186. Alessandrello MJ, Parellada EA, Tomás MSJ, Neske A, Vullo DL, et al. (2017) Polycyclic aromatic hydrocarbons removal by immobilized bacterial cells using Annonaceous acetogenins for biofilm formation stimulation on polyurethane foam. Chem Engineer5: 189-195.
187. Islam MS, Ahmed MK, Raknuzzaman M, Habibullah-Al-Mamun M, Kundu GK (2017) Heavy metals in the industrial sludge and their ecological risk: A case study for a developing country. J Geochem Explor 172:41-49.
188. Uddin MK (2007) A review on the absorbtion of heavy metals by clay minerals, with special focus on the past decade. Che Enginee J 308: 438-462.
189. Hamza UD, Mohammed IM, Sale A (2012) Potentials of bacterial Isolates in bioremediation of petroleum refinery wastewater.J Appl Phytotechnol 1: 131-138.
190. Malik ZA, Ahmed S (2012) Degradation of petroleum hydrocarbons by oil field isolated bacterial consortium. Afr J Biotechnol 11: 650-658.
191. Phan CW, Bakar NF, Hamzah A (2013) Comparative study on bio surfactant activity of crude oil- degrading bacteria and its correlation t total petroleum hydrocarbon degradation. Biorem J 17: 240 -251.
192. Abdin BA (2017) Bioremediation of polycyclicaromatic hydrocarbon compounds and some heavy metals .poulluted petroleum wastewater. Sc. Thesis Fac. Sci. Helwan Univ., Cairo, Egypt.
193. Hassan MFA (2017) Enhancement of microbiological and physicochemical treatment of petroleum wastewater.D. Thesis Fac. Sci. Cairo Univ. Giza, Egypt.