| Polycyclic aromatic hydrocarbons (PAHs) compose a large and heterogeneousgroup of organic contaminants. It contains compounds with two to six rings, fused ina linear, angular, or cluster arrangement. PAHs are formed and emitted as a result ofthe incomplete combustion of organic material. They may be also released into theenvironment through the disposal of coal tars and other coal processing wastes,petroleum sludges, asphalts, creosote and other wood preservative wastes, chemicalwastes, and soots. The fate of these compounds and their degradation products in theenvironment is of concern due to their toxic, mutagenic, and carcinogenic properties.Sixteen PAHs are listed as priority pollutants by the US Environmental ProtectionAgency.Microbes play an important role in bio-remediation technologies, so that it is abasic study to find out efficiently functional strains for environmentalbio-remediation. In this paper four PAHs-biodegrading strains were been screenedwith a selective culture medium of PAHs from oily wastewater andoil-contamination soil. The four strains were been identified through morphological,physiological and biochemical characteristics investigation and gene analysis. The16S rDNA of the strains were amplified by PCR and was sequenced 581, 582, 1209,1230 bp respectively, and then were compared with those available in the GenBank databases. The results show that 3-28 16S rDNA sequence is most similar to that ofMicrobacterium esteraromaticum, NF similar to Cellulosimicrobium cellulans, EWsimiar to Chelatococcus asacharovorans, EY similar to Sphingopyxis terrae, and thesequence similarities are 100%, 97.8%, 98.2% and 99.0%, respectively. The fourstrains belong to Microbacterium, Cellulosimicrobium, Chelatococcus andSphingopyxis sp. The phylogenetic trees including the four strains were derivedwith DNAMAN and analyzed with Bootstraping. The results demonstrate that 3-28,NF, EW and EY strains were close consanguinity to Microbacterium sp.,Cellulosimicrobium sp., Chelatococcus sp. and Sphingopyxis sp.Enzymes and their metabolic products in PAHs bidegradation process havebeen analyzed to determine the possible reduction trajectories of PAH-biodegradingstrains. The results show that the activities of dehydrogenase and polyphenoloxidase can be examined during the reduction process of PAHs, and the reductionprocess is influenced somehow by the two enzymatic systems. However,dehydrogenase and polyphenol oxidase seems not to be the principal enzymaticsystems in the PAHs biodegradation. In fact, the results indicate that bioxygenasesystem plays an important role in the ring cleavage process, i.e., all of metabolismsof phenanthrene, anthracene a pyrene result from bioxygenase system mostly, anddihydroxy-PAHs can also be detected in all of their metabolite.One of the mechanisms of microbial enhanced oil recovery (MEOR) is toutilize microbes to biodegrade the heavy fractions of crude oil such as the resins andasphaltene and reduce its viscidity and freezing point in order to improve thephysicochemical characteristics of the thicked oil. A strain of Microbacterium sp.was screened to biodegrade the asphaltene fraction of the crude oil from Bohai oilfield and Xinjiang oil field effectively and the change of the components among thesaturated fraction, aromatic fraction, resins and asphaltene fraction and theircomposition were analyzed. The results show that the physicochemicalcharacteristics of the crude oil have been changed obviously under the effect ofMicrobacterium that the contents of the resin and asphaltene fraction decrease above 9% and the saturated and aromatic fraction increase to a certain extent and theviscidity and the freezing point reduce 15% and 20% respectively.
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