DEGRADATION OF CRUDE OIL BY MIXED CULTURE

Four bacterial strains (X2、X3、X4、X5) which could degrade oil effectively were separated from oil-polluted water. The strains were identified as Xanthomonas sp. , Zoogloea sp. , Bacillus sp. , and Plesiomonas sp. The growth of the community in a medium containing crude oil as carbon source was observed to determine the predominant strain. The oil-degradation effects of various combination of the strains were confirmed by the mixed experiment of two, three or four strains randomly, and the optimal dosage of every strain was studied with the method of orthogonal experiment. Using the techniques of GC - MS, the effect of every strain on degrading crude oil was analyzed. The results showed that X4 was the predominant strain. X4 it could degrade 68. 60% of crude oil, and the other three strains could also degrade 63. 17% of crude oil after mixed. The existence of strain X4 was the key to attain high rate of oil-degradation of mixed culture. The best degrading effects would be obtained when four strains were inoculated 0.1% , 0.1% , 0. 5% , 2. 0% , respectively. Strains X2 and X3 could degrade C12-C16 straight chain alkanes and some branched ones, while strain X4 and X5 could degrade C12-C22 straight chain alkanes. Fig 2, Tab 4, Ref 10