Isolation And Identification Of Strains Efficiently Degrading Heavy Oil And Their Degradation Characteristics

The environmental problems caused by petroleum contamination had focused worldwide concern in the past decades. Heavy oil is one type of petroleum hydrocarbons, whose composition is very complex. It has high resin and asphaltene content, also has high density and viscosity. With the increasing use of heavy oil, the pollution incident on the environment is gradually increasing. It is a focus at present that microorganism is very important to deal with the heavy oil pollution. Isolation and identification of heavy oil degradation strains and further study on their degradation characteristics are feasible ways to treat heavy oil-contaminated environment.Two bacterial strains named GS02 and GS07 degrading heavy oil were enriched and screened from oil sludge collected from Sinopec Guangzhou Company. Both of the two strains were identified as Acinetobacter sp. by a series of morphological and biochemical characteristics and 16S rDNA sequencing sequences analysis. Preliminary studies of the bacterial growth, the degradation rate and the effect of environmental parameters on the heavy oil degradation were conducted in shaking flasks using heavy oil as the sole carbon source. The degradation rate of 1g/L heavy oil was 45.3% and 46.1% by GS02 and GS07 after 5 days, respectively. The degradation rates of the heavy oil reduced with the increasing of the initial heavy oil concentration. The optimum degradation temperatures were 28 oC and 30 oC, the optimum pH were 7.0 and 7.2, and the optimum salt concentrations were 4-6 g/L and 4g/L for strain GS02 and GS07, respectively.The residual heavy oil was analyzed by gas chromatography-mass spectrometry (GC-MS) and results showed both strains GS02 and GS07 had good ability to remove alkanes as well as biomarker compounds such as pristine (Pr) and phytane (Ph). The degradation rates of Pr and Ph in 5d were 72.5% and 77.76%, respectively. The asphaltenes after degradation was analyzed by FTIR and results showed the -CH3 and -CH2- absorption peak intensity decreased and the number of the heterocyclic and aromatic decreased, which further indicated that strains GS02 and GS07 had a good degradation ability on heavy oil. The surface tension of medium was determined during the GS02 and GS07 degradation process. Results showed there was no evident change in the medium containing GS02, however, the surface tension in the medium containing GS07 had decreased from 68.5 mN·m-1 to 46.2 mN·m-1 which indicated strain GS07 has a certain emulsification on heavy oil.