Isolation Of Hydrocarbon Degraging Bacteria And The Study Of Degrading Condition

Using diesel oil as the only carbon source, and domesticated gradually, a bacterial consortium with high hydrocarbon degrading ability were obtained from oil-polluted sediments(oil content 0.2 g/g) in intertidal zone of Tianjin seashore. Several bacterial strains were isolated by viable culturing. Two of them strain H1 and strain H2 were identified by 16s rDNA sequence analysis, belonging to Pseudomonas sp. and Thalassospira sp., respectively. Through degradation experiments, we studied the effect of organic nitrogen source on biodegradation and found the optimal yeast extract concentration. By contrasting the biodegradation and GC-MS determination during a period of 30 days, using organic and inorganic nitrogen source, yeast extract and (NH4)2SO4 , respectively, we found the biodegradation was accelerated under the condition of yeast extract, simultaneously, their degrading mechanisms were also analysed and discussed.The results of experiments as follows:(1)The isolated hydrocarbon degrading bacteria consortium can adapt a wide salinity range from 1% to 7%. The optimal salinity is 3.5%, which is analogous to the salinity of sewater.(2)Using yeast extract as the nitrogen source , the condition which can accelerate the biodegradation is yeast extract 8.0 g/L, diesel oil 1%(V/V), FePO4·4H2O 6.0 mg/L without adjusting the pH, inoculum quantity 2%(V/V), 26℃and 150 rpm.(3)Through contrast experiment, we found the ultimate biodegradation efficiency are same during 30 days, but under the condition of using yeast extract the biodegradation were accelerated almost decuple than that of (NH4)2SO4. The reason is that yeast extract not only supply nitrogen source, but also offer easily accessible carbon and other nutrients to increase the biomass in the initial phase, so enhancing the microbial degradation of diesel oil. In addition, NH3 produced by metabolism of yeast extract is the buffer in the microbial degradation system, which can stabilize pH in the low alkaline environment for the full growth of bacteria. Consequently, compared with the conventional inorganic nitrogen source, yeast extract is superior.In the study, the hydrocarbon degrading bacteria consortium can degrade diesel oil (≤1%) completely in 3 days using yeast extract as the nitrogen source.