Enhanced biodegradation of crude oil by constructed bacterial consortium comprising salt-tolerant petroleum degraders and biosurfactant producers

Bioremediation is an attractive strategy of utilizing bacteria to remove crude oil contaminants. In this study, two salt-tolerant crude oil-degrading and biosurfactant-producing bacteria, Dietzia sp. CN-3 and Acinetobacter sp. HC8-3S, were functionally combined to construct a bacterial consortium. The consortium achieved 95.8% degradation efficiency of crude oil in 10 days and various n-alkanes, cycloalkanes, branched alkanes and aromatic hydrocarbons were all depleted more effectively than single strains. Functional optimization of the consortium degraded crude oil efficiently in a wide range of pH (4-10) and salinity (0-120 g L-1). Furthermore, two alkane hydroxylase genes, alkB in CN-3 and alkM in HC8-3S, were cloned and their expression were examined by real-time quantitative polymerase chain reaction, indicating that alkB was more prominent in long-chain alkanes (C-20, C-24 and C-26) utilization and alkM played crucial roles in medium- and long-chain alkanes (C-14, C-16, C-20, C-24 and C-26) degradation. In soil microcosms artificially contaminated with crude oil and bioaugmented with the consortium, 58.3% of total petroleum hydrocarbons were depleted after 60 days and the degradation rate (485.8 mg kg(-1) d(-1)) was higher than those reported in previous studies. Consequently, the consortium is a promising candidate in crude oil bioremediation.