Simultaneous immobilization enhances synergistic interactions and crude oil removal of bacterial consortium.

Oil spillage has serious adverse effects on marine environments. The degradation of crude oil by microorganisms may be an effective and sustainable approach. In this study, the removal of crude oil from seawater by immobilized bacterial consortium was performed and the enhancement of crude oil degradation efficiency by varying immobilization methods and inoculum volume ratio was examined. The nonpathogenic and heavy metal-tolerant bacterial consortium of Sphingobium naphthae MO2-4 and Priestia aryabhattai TL01-2 was immobilized by biofilm formation on aquaporousgels. The simultaneous immobilization of strains MO2-4 and TL01-2 showed better crude oil removal efficiency than independent immobilization, which indicated positive interactions among consortium members in the mixed-culture immobilized systems. Moreover, the immobilized consortium at a 2:1 (MO2-4:TL01-2) inoculum volume ratio showed the best crude oil removal capacity. The immobilized consortium removed 77% of 2000 mg L-1 crude oil in seawater over 7 days. The immobilized consortium maintained crude oil removal efficacy in semicontinuous experiments. In addition, the immobilized consortium was used to remediate seawater contaminated with 1000 mg L-1 crude oil in a 20 L wave tank. After 28 days, the crude oil degradation efficiency of immobilized consortium was approximately 70%, and crude oil degradation through natural attenuation was not observed. Moreover, the genomic features of strains MO2-4 and TL01-2 are reported. Genomic analyses of both strains confirmed the presence of many genes involved in hydrocarbon degradation, heavy metal resistance, biosurfactant synthesis, and biofilm formation, supporting the biodegradation results and characterizing strain properties. The results of this work introduce the potential benefit of simultaneous immobilization of bacterial consortia to improve efficiency of crude oil biodegradation and has motivated further investigations into large-scale remediation of crude oil-contaminated seawater.

16S metagenomic analysis reveals adaptability of a mixed-PAH-degrading consortium isolated from crude oil-contaminated seawater to changing environmental conditions.

A bacterial consortium, named SWO, was enriched from crude oil-contaminated seawater from Phrao Bay in Rayong Province, Thailand, after a large oil spill in 2013. The bacterial consortium degraded a polycyclic aromatic hydrocarbon (PAH) mixture consisting of phenanthrene, anthracene, fluoranthene, and pyrene (50 mg L-1 each) by approximately 73%, 69%, 52%, and 48%, respectively, within 21 days. This consortium exhibited excellent adaptation to a wide range of environmental conditions. It could degrade a mixture of four PAHs under a range of pH values (4.0-9.0), temperatures (25 °C-37 °C), and salinities (0-10 g L-1 with NaCl). In addition, this consortium degraded 20-30% of benzo[a]pyrene and perylene (10 mg L-1 each), high molecular weight PAHs, in the presence of other PAHs within 35 days, and degraded 40% of 2% (v/v) crude oil within 20 days. The 16S rRNA gene amplicon sequencing analysis demonstrated that Pseudomonas and Methylophaga were the dominant genera of consortium SWO in almost all treatments, while Pseudidiomarina, Thalassospira and Alcanivorax were predominant under higher salt concentrations. Moreover, Pseudomonas and Alcanivorax were dominant in the crude oil-degradation treatment. Our results suggest that the consortium SWO maintained its biodegradation ability by altering the bacterial community profile upon encountering changes in the environmental conditions.