Biodegradation of crude oil by a moderately haloalkaliphilic Acinetobacter strain

Bioremediation of crude oil (or petroleum) pollution in the saline-alkali environment is challenging due to the lack of halotolerant and alkali tolerant oil-degrading bacteria. It is shown here that a newly isolated Acinetobacter strain D2 able to degrade crude oil was moderately haloalkaliphilic. Physiological characterization showed that the optimal crude oil degradation conditions for D2 strain occurred at pH = 9 and NaCl concentration of 2% w/v. Moreover, D2 can tolerate pH 11 and NaCl concentration of 8% w/v. Kinetic analysis indicated that crude oil (0.2% and 0.5% w/v) biodegradation by D2 followed the first-order kinetic model, with the k constant estimated as 0.089-0.111 d(-1) and the half-life period of petroleum degradation as 6.24-7.79 d. The results of the gas chromatographic analysis revealed that strain D2 could degrade most saturated hydrocarbons, with higher removal efficiencies for shorter-chain alkanes. Strain D2 can also remove aromatic hydrocarbons with an average efficiency of 33.4%. Combined, these results demonstrated that a moderately haloalkaliphilic Acinetobacter strain can be a suitable candidate for bioremediation of oil-contaminated saline soil and oilfield produced water.