Study On Construction Of High-effective Microbial Consortium And Immobilized For Degrading Crude Oil

With the oil pollution becoming more and more serious, biodegradation has become an important method for controlling the oil pollution, because it is efficient and pollution-free. Oil is a complex mixture which composed of saturated hydrocarbon, aromatic compounds, some asphaltene and resin. Single strains have limited ability of metabolizing oil components, so it is difficult to completely remove the oil from the environment. The synergies of mixed strains help to improve the ability of degradation. Therefore, the research focus is how to use the interaction between different strains to build a reasonable and efficient degradation flora. Immobilized microorganism technology can enhance oil degradation by keeping high density micro-organisms and biological activity.In this study, the alkane degrading bacteria GS3C, phenanthrene degrading bacteria GY2B and pyrene degrading bacteria (GP3A and GP3B) were domesticated by crude oil. The results show that these strains can grow and metabolize by using crude oil as sole carbon source. So they can degrade crude oil and the removal ratio reaches 30%. GC-MS analysis shows that GS3C can basically remove the straight-chain alkane compounds in crude oil. GY2B has a good degradation of the aromatic compounds. GP3A can remove the short-chain alkanes and aromatic compounds and GP3B have less degradation of alkanes and aromatic compounds.Efficient mixed strains were constructed by using these four strains. The optimal mixed strains G8 was selected and its oil removal ratio is 68.76%, nearly 30% higher than the single strains. The GC-MS analysis indicated that G8 retained the degradation characteristics of GS3C and GY2B. It can basically remove the alkane compounds in crude oil and has a good degradation on the aromatic compounds. Through the joint of three kinds of strains, mixed strains G8 have more capacity of degrading the crude oil.The results show the best mixing ratio of mixed bacteria G8 is GS3C:GY2B:GP3B= 1:1:1. The removal efficiency of combination G8 reached 69.20% in 5 days when the initial crude oil concentration was 2000 mg/L, which was 30% higher than that of individual bacterial strain. The optimum conditions for G8 growth were 30℃,initial pH 7, and 4% inoculation volume.The mixed strains G8 was adsorbed and immobilized by rice straw and corn stalks. The results showed that the immobilized strains have better removal of oil than free strain or the mixture of carrier and strains and the no-sterilized straw have better removal of the oil than sterilization one. The mixed strains G8 which immobilized by rice straw was removed 90%～95% of oil. The one immobilized by corn stalk was removed 95%～98% of oil, nearly 40% higher than the one by non-immobilized G8 . The non-sterile corn stalks as the best carrier, the removal of crude oil reached 98.19 %.