Studies on degradation mechanism of petroleum under anoxic condition.

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Bacterial strain HD-1, isolated from an oil field, is able to degrade both aliphatic and aromatic hydrocarbons anaerobically. In this project, bacterial degradation mechanisms of petroleum under anoxic condition was studied Utilizing tetradecane (alkane) as a substrate, two kinds of alkene were accumulated as degradation intermediates in HD-1 cells. Finally a main component of the alkenes was identified as 1-dodecene based on analyzes data from FT-IR,1H-NMR,and GC/MS.This result shows that alkane is dehydrogenated by the strain HD-1 under anoxic condition. Although one example was reported in 1992 from a research group in Germany about alkane degradation under anoxic condition, this is the first report on the structural analysis of a degradation intermediate. Moreover, strain HD-1 were found to be able to grow on CO2 as a sole carbon source and produce alkane in the cells. Its production yield was 0.1% in dry cell weight. The metabolic pathway from CO2 to alkane needs to be elucidated in a future.Recently, a new bacterial strain TK-122 was isolated oil-reservoir tank. Its oil degradation ability is superior to HD-1 under both oxic and anoxic conditions. About 70% of alkanes (from octane to hexadecane) in petroleum, was degraded in 3 days under anoxic condition. Molibdenate (MoO4^<2->) was used as an electron acceptor in the anaerobic degradation of alkane. This result indicates a finding of a new petroleum degradation pathway. According to the analysis on 16S rRNA nucleotide sequence of the strain TK-122, Escherichia or Citrobacter was most probable genus. However, physiological characterization of the strain matched with none of these genera. It is indicated that the strain TK-122 belongs to a new genus.