Hydrocarbonoclastic biofilms based on sewage microorganisms and their application in hydrocarbon removal in liquid wastes

Abstract

Attempts to establish hydrocarbonoclastic biofilms that could be applied in waste-hydrocarbon removal are still very rare. In this work, biofilms containing hydrocarbonoclastic bacteria were successfully established on glass slides by submerging them in oil-free and oil-containing sewage effluent for 1 month. Culture-dependent analysis of hydrocarbonoclastic bacterial communities in the biofilms revealed the occurrence of the genera Pseudomonas, Microvirga, Stenotrophomonas, Mycobacterium, Bosea, and Ancylobacter. Biofilms established in oil-containing effluent contained more hydrocarbonoclastic bacteria than those established in oil-free effluent, and both biofilms had dramatically different bacterial composition. Culture-independent analysis of the bacterial flora revealed a bacterial community structure totally different from that determined by the culture-dependent method. In microcosm experiments, these biofilms, when used as inocula, removed between 20% and 65% crude oil, n-hexadecane, and phenanthrene from the surrounding effluent in 2 weeks, depending on the biofilm type, the hydrocarbon identity, and the culture conditions. More of the hydrocarbons were removed by biofilms established in oil-containing effluent than by those established in oil-free effluent, and by cultures incubated in the light than by those incubated in the dark. Meanwhile, the bacterial numbers and diversities were enhanced in the biofilms that had been previously used in hydrocarbon bioremediation. These novel findings pave a new way for biofilm-based hydrocarbon bioremediation, both in sewage effluent and in other liquid wastes.