[Isolation identification and characterization of halotolerant petroleum-degrading bacteria]

To obtain efficient halotolerant petroleum-degrading bacteria, 39 bacteria strains were isolated from 30 petroleum contaminated saline soil samples in Yellow River Delta, an important base of petroleum production in China. One bacterium (strain BM38) was found to efficiently degrade crude oil in highly saline environments based on a series of liquid and soil incubation experiments. According to its morphology, physiochemical characteristics and 16S rDNA sequence analysis, this strain was identified as Pseudomonas putida. Moreover, a series of liquid incubation experiments were conducted to investigate its characteristics such as halotolerance, biosurfactants production and degrading efficiency for various hydrocarbons. The salt resistance test demonstrated that strain BM38 grew well at NaCl concentrations ranging from 0.5% to 6.0%. Petroleum degradation experiments showed that strain BM38 could degrade 73.5% crude oil after 7 days in a liquid culture medium containing 1.0% NaCl and remove more than 40% of total petroleum hydrocarbons after 40 days in the soil with 0.22% and 0.61% of salinity, these results proved that the strain was effective in removing petroleum hydrocarbons. Strain BM38 could produce a bioemulsifier in a liquid culture medium. The NaCl concentration had the significant effect on the EI24 of fermentation broth, which decreased sharply if the NaCl concentration was greater than 1.0%. However, the EI24 of BM38 was still quite high in the presence of 2.0% of NaCl, and the value was 61.0%. Furthermore, this strain was also able to grow in mineral liquid media amended with hexadecane, toluene, phenanthrene, isooctane and cyclohexane as the sole carbon sources. Among these hydracarbons, strain BM38 showed relatively high ability in degrading n-alkanes and aromatic hydracarbons. The results indicated that strain BM38 had potential for application in bioremediation of petroleum-contaminated saline soil.