Screening of highly efficient petroleum-degrading bacteria and their biodegradation characteristics

Three strains of bacteria,identified as Pseudomonas sp.(GX1),Plesionmonas sp.(GX2) and Zoogloea sp.(GX3),for degrading oil with high efficiency were isolated from oil-contaminated soil.And the optimum ecological conditions for their degrading were studied by changing the pH value,the nutrients and the mass concentration of the oil.The testing results show that if the pH value was in the range of 7 to 9,the biodegrading efficiency of the three strains can reach to 86.7%,72.9% and 64.7% respectively.The ammonium nitrate(NH_4NO_3)was demonstrated as the optimum nitrogen source and the optimum ratio of nitrogen over phosphorus was 4 over 1.The degrading efficiency will increase a little with the increasing of the oil concentration under low initial oil concentration.Different strains have different degrees of oil tolerance.