Carrier mounted materials with bacterial consortia can facilitate oil biodegradation

Carrier mounted bacterial consortium facilitates oil remediation in the marine environment

Simons et al 2013

Oil pollution in the marine environment is a serious environmental hazard and the impact of the long term presence of oil upon the oceans’ ecosystem remains unknown. Weathered oil is persistent in the environment due to recalcitrant compounds with a high molecular weight that are not easily removed or degraded. Removal of oil from the marine environment is a difficult task. Often this results in either more chemicals applied (dispersants added to assist in the removal of the oil) or the presence of large amounts of oil remaining in the form of weathered oil. Removal of oil from the marine environment is a difficult task. Often this results in either more chemicals being applied, (dispersants added to assist in the removal of the oil) or the presence of large amounts remaining as weathered oil. Microbial degradation of hydrocarbons occurs at the hydrocarbon/water interface as it is essential for microbes to have direct contact with hydrocarbons. Studies have demonstrated the effectiveness of carrier materials to enhance degradation, this combines bio-augmentation and bio-stimulation in a complementary manner to deliver both microbes and nutrients to an oil-contaminated region of the ocean. In this study, Simons et al investigated the capacity of two cost effective and sustainable materials (shell grit and alginate) that contained additional nutrients as carriers to dispense a concentrated bacterial consortia consisting of 6 novel hydrocarbon degrading strains in a laboratory tank mesocosm. Furthermore, they assessed the two carrier materials to determine which was the most efficient in terms of degrading weathered oil. Finally, they looked to see if any toxic substances were produced.  

This is the first study that directly assessed the efficacy of two carrier materials that had been bio-augmented and bio-stimulated. The shell grit material significantly reduced the presence of hydrocarbons, resulting in 75% degradation whereas the oil degradation shown by the alginate was 20%. This indicated that not only was the shell grit an economical and sustainable material, it is the most effective in the removal of hydrocarbons. The weathered oil applied in this study had a strong presence of high chain (>32C) hydrocarbons, indicating that recalcitrant compounds like PAH’s may have been degraded but this was not tested. Also the authors highlight that there may have been efficacy issues in the bacterial consortia’s access to hydrocarbon on the alginate because it was immobilised. In contrast, the bacterial consortia were not immobilised onto the shell grit, so their exposure was not limited, to the best of my knowledge they did not justify why this was done, so it could be argued that these results may not be comparable. To determine if the presence of carrier materials caused an immediate change in the diversity of microbial communities, the four tanks were assessed by DGGE, this showed that there was no change to the original consortia, indicating that these could be successfully implemented in the wild.

So in summary this study demonstrated the effectiveness of shell grit as a carrier material in the remediation of marine weathered oil. The shell grit material significantly reduced (75%) the presence of the weathered oil. There was also a significant amount of degradation of the contaminant oil in the presence of the nutrients and bacterial consortia. However, this is a lab study, so the results are limited. The effects of environmental factors need to considered for future based field studies. The carrier materials applied is this study did not significantly influence the indigenous marine microbe population, as determined by DGGE assessment. The ecotoxicity data also supported the application of the shell grit carrier material as an effective remediation method. Future studies will be required to further develop this remediation method to address the unique problems associated with marine water remediation.

http://www.sciencedirect.com/science/article/pii/S0960852413001843