Abstract: Pollution of diesel has posed a huge threat to human health and ecological environment, the microbial bioremediation has become a common method for controlling diesel pollution. In this experiment, 35 strains were found to have ability to decompose diesel by culturing with diesel as the sole carbon source. Then, one diesel fuel-degrading halophilic bacteria, B-18, was selected using measurement of degradation rate of diesel. By measuring surface tension, oil drain ring diameter and performing immunohemolysis experiments, B-2 was screened out, which was a biosurfactant producer. B-2 showed a degradation rate of 44.80% with 3% diesel, the diameter of the oil drain ring was 6 cm and the surface tension was reduced from 74.88 mN·m^-1 to 27.15 mN·m^-1, which was identified as Salimicrobium sp. The degradation rate of B-18 for 3% diesel was 54.00%, which was identified as Salinicoccus sp. The result of GC-MS showed that the bacteria could degrade alkanes with a carbon chain length of 14-29. When the concentration of diesel was 5%, the degradation rates of B-2 and B-18 in GM could be increased from 35.52% and 45.62% to 49.08% and 53.46%. The degradation rate by microbial consortium composed of B-2 and B-18 strains could reach 68.50%. The microbial consortium was able to degrade the diesel by 70.45% under optimized conditions, referring to NaCl concentration 100 g·L^-1, 37 ℃, pH 7.5. Through scanning electron microscopy (SEM), it was found that B-2 and B-18 had typical morphological changes during the degradation of diesel, and the surface of halophilic bacteria could form sticky substances that to interconnect the individual cells, which accelerated the absorption and degradation of diesel. In high-salt environments, the microbial consortium could be used for bioremediation of diesel contaminated environments.

Key words: halophilic, biosurfactant, diesel-degrading bacteria, degradation characteristics