Crude oil removal by Sphingobium sp. MO2-4 and Bacillus megaterium TL01-2 immobilized on aquaporous gel

Abstract

Petroleum products are the major energy sources that drive global economy. The exploration and exploitation of crude petroleum oil increase the potential risk for oil spills in marine ecosystem. In this work, two non-pathogenic sponge-associated bacteria were developed as immobilized bacterial co-culture for crude oil removal from seawater. Two bacteria were Spingobium sp. MO2-4 that could degrade crude oil, diesel oil, and fuel oil, and Bacillus megaterium TL01-2 that could degrade crude oil, possessed high cell surface hydrophobicity, could tolerate heavy metal, and was able to form biofilm.. The modified polyurethane foam, aquaporous gel (AQ), was used as carrier for the bacteria. The crude oil removal from actual seawater by immobilized bacteria was carried out in three groups based on immobilization process. With the initial crude oil concentration of 2,000 mg/L, the result showed that immobilization of the bacteria as co-culture using 2:1 (MO2-4:TL01-2) inoculum volume ratio yielded the best result with 1,757 mg/L of crude oil removed and 1,427 mg/L was degraded within 7 days, thus the ratio was chosen for further use in the semi-continuous system and wave simulator tank. The semi-continuous system study revealed the better performance of immobilized bacteria over the free cell; in addition, the immobilized bacteria survivability throughout the experiment was confirmed by viable plate count and Scanning Electron Microscope (SEM). The wave simulator tank containing 20 L seawater was used to simulate the removal of oil spill by immobilized bacteria in marine environment. The result revealed that the immobilized bacteria could remove more than 90% of crude oil within 7 days. Furthermore, when compared the amount of crude oil accumulated in AQs from the immobilized bacteria treatment and sterilized AQs treatment at the end of experiment; the result showed that the immobilized bacteria could degrade 72% of the absorbed crude oil. Accordingly, these results suggested that the immobilized bacteria is a promising tool for bioremediation of crude oil-contaminated marine environment.