Benzene and Toluene Biodegradation Potential in Methanogenic Cultures Established by Feeding Benzene, Toluene and their Mixture

Abstract

Benzene and toluene often contaminate groundwater and pose serious threat to human health due to their high toxicity. Anaerobic degradation can be a cost-effective method but the degradation mechanism remains poorly understood. We established benzene- and/or toluene-degrading bacterial cultures under methanogenic conditions from non-contaminated soil to compare their behaviour during and after enrichment. Benzene and toluene degradation rates increased during incubation, and this fact implied enrichment and/or adaptation of benzene/toluene-degrading microorganisms. The abundance of Hasda-A and/or related bacteria, defined by a primer set targeting uncultured putative benzene-degrading Desulfobacterales bacterium Hasda-A, increased only in the enrichments fed with benzene. This result indicated that Hasda-A and/or related bacteria played an important role on benzene degradation. Furthermore, to investigate the biodegradation range of benzene and toluene degraders, we added both benzene and toluene to all cultures. Toluene or benzene was also degraded by cultures that have been fed with benzene or toluene, respectively. The culture which was originally fed only with toluene had smaller benzene degradation rate than the culture fed with benzene. Similar result was obtained for toluene degradation in cultures fed with toluene or benzene. These data indicate that different microorganisms were likely involved in benzene and toluene degradation in our enrichments.