Diversity Of Halophilic Bacterial Consortiums From Oil-Polluted Soil And Their Biodegradation Characteristics Of BTEX

In this study, the saline contaminated soil were collected at different sites in shengli oilfield, and were used to inoculate in two gradient of salinity: 5% and 10%. In paralled, the bacterial community were obtained in two methods: enrichment(E) and domestication(D).The structure and diversity of the bacterial communities were analyzed by using PCR-DGGE technique. The result shows lower diversity of the bacterial community from long-term polluted soil than for those from consequently contaminated soil, and higher diversity of the bacterial communities by enrichment process than those obtained by domestication. The concentration of TPH (1.58%-10.85%) of the soil and the gradient of salinity used in the enrichment don't affect much to the bacterial diversity. 16S rRNA gene analysis revealed that the dominant sequences from DGGE profile of the bacterial consortiums were related to halophilic or halotolerant bacterial groups, such as Marinobacter, Halomonas, Alcanivorax and Bacillus. The existences of those bacteria do greatly enhance the degradation ability of the bacterial consortiums. To further characterize the bacterial communities, bacterial strains were isolated. Phylogenetic analysis of some strains showed they are related to some halophilic or halotolerant strains in genus Bacillus.The study investigates the biodegradation characteristics of the bacterial consortiums and finds out the effect of environmental factors on the degradation ability. The result shows that the degradation ability increases in direct proportion to the community diversity. The consortiums obtained by domestication show better degradation rate at lower salinity (≤5%), while the consortiums obtained by enrichment perform better at higher salinity (≥5%). In the other hand, the consortiums obtained from 5% salinity are effective with a wider salinity range. And the bacterial consortium obtained from 5% salinity by enrichment (No.5s-4) shows best biodegradation ability than other consortiums. The consortiums'ability of degrading BTEX and PAH could be enhanced markedly by the addition of low concentration of yeast extract (YE). The optimum degradation occurred at pH 7.5 and 30℃. The consortium could also degrade benzene at 45℃.The study further investigates the degradation characteristics of No.5s-4 consortium. The consortium could totally degrade benzene or toluene in 96 hours, when the substrate concentration is 20mg/L-400mg/L. The high concentration of substrate doesn't poison the consortium. Furthermore it could totally degrade BTEX or BT mixtures under 20mg/L-400mg/L within 112 hours. The study also found out the enrichment culture could degrade 47.96% phenanthrene within 11 days, while the consortium obtained from domestication shows better result with 100% degradation rate. The degradation ability of the bacterial community is higher than pure bacterium.