Biodegradation of n-alkanes in crude oil by three identified bacterial strains

In this study, aerobic biodegradation of crude oil was simulated using Pseudomonas aeruginosa XJ16, Bacillus cereus XJ20, and Acinetobacter lwoffii XJ19 bacteria for 90 days, for semi-quantitative calculation of concentration, demonstrating that n-alkanes (C14–C35) were biodegraded by the three strains at different ratios and rates. P. aeruginosa XJ16 showed the highest biodegradative potential for n-alkanes, with total biodegradation ratio of 98.2% in 10 days. In comparison, the total biodegradation ratio by B. cereus XJ20 increased gradually and achieved 98.8% after 90 days; whereas that by A. lwoffii XJ19 was much lower even after 90 days (29.3%). In addition, P. aeruginosa XJ16 and B. cereus XJ20 exhibited stronger biodegradation efficiencies for C18–C32 n-alkanes (95.4%–99.7%) than A. lwoffii XJ19 (9.05%–73.0%). However, all three bacterial strains exhibited comparably good biodegradation efficiencies for C33–C35 n-alkanes (60.2%–86.4%). Moreover, the biodegradation rate constants and biodegradation rates were of the decreasing order: P. aeruginosa XJ16 > B. cereus XJ20 > A. lwoffii XJ19. P. aeruginosa XJ16 and B. cereus XJ20 biodegrade n-alkanes with relatively low carbon numbers more easily than those with high carbon numbers. However, A. lwoffii XJ19 is more likely to biodegrade n-alkanes with relatively high carbon numbers. On day 10, surface tension (mN·m−1) declined from 70.6 to 35.9 by treatment with P. aeruginosa XJ16, to 31.3 with B. cereus XJ20, and to 34.1 with A. lwoffii XJ19. As biosurfactant-producing and hydrocarbon-degrading bacteria, these three strains have the potential to be used for bioremediation of hydrocarbon pollutants.