Biotransformation of Aliphatic and Aromatic Hydrocarbons by Aerobic Bacterial Strains Isolated from Brown Coal

Lignite collected from a brown coal deposit was colonized with fully aerobic bacteria exhibiting hydrocarbon biodegradation pathways. Six autochthonous strains were isolated and tested for tolerance and biotransformation potential towards various xenobiotics such as hexadecane, squalane, pristane, benzoic acid, naphthalene, phenanthrene, and diesel oil. After preliminary screening, four xenobiotic-resistant strains were selected (<i>Rhodococcus opacus</i> CUP11, <i>Pseudomonas fluorescens</i> CUP15, <i>Sphingobacterium</i> sp. CUP16, and <i>Rhodococcus</i> sp. CUP17) and further treated for 14 days under aerobic conditions with variant concentrations of each compound (1, 2.5, 5 and 10 g/dm³). Microbial population dynamics and xenobiotic level changes were monitored. <i>Rhodococcus opacus</i> CUP11 and <i>Rhodococcus</i> sp. CUP17 were the most metabolically versatile bacteria capable of biotransforming several xenobiotics. Among the best-performing strains, the highest degradation yields were obtained for CUP17 (81% removal of diesel oil applied at 10 g/dm³, 99% of 2.5 g/dm³ hexadecane and 27% of 1 g/dm³ squalane), and CUP11 (49% of 10 g/dm³ hexadecane and 48% of 1 g/dm³ pristane). The strain CUP16 utilized squalane (33% at 1 g/dm³). The results suggest that the lignite-indigenous bacteria may be applicable for bioremediation of persistent xenobiotics in environmental cleanup projects.