Characterization of an enrichment culture debrominating tetrabromobisphenol A and optimization of its activity under anaerobic conditions

Abstract

To study the effects of incubation conditions on the microbial community structure and activity of a TBBPA-debrominating enrichment culture composed of bacterial and archaeal species. The effects of the methanogen inhibitor 2-bromoethanesulfonate (BES), of the antibiotic ampicillin, of substrate (tetrabromobisphenol A, TBBPA) omission and availability of different electron donors on microbial community structure and activity were examined under anaerobic conditions. Debromination of TBBPA was blocked in the presence of ampicillin, while long-term incubation with BES resulted in delayed debromination activity. The results suggest that the bacterial species responsible for the debromination of TBBPA, while archaeal species involved in electron donor metabolism. The enrichment culture lost its debromination activity after cultivation for 9 months without TBBPA, concomitantly with the disappearance of two DNA bands in a denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene fragments corresponding to Pelobacter carbinolicus and Sphaerochaeta sp. TQ1 that were present in the original culture. When butyrate was used as an electron donor, TBBPA debromination activity was attenuated. When acetate was used as the electron donor, no debromination was observed and in addition, there was a decrease in the abundance of the mcrA gene. The results indicate that to maintain a high rate of TBBPA debromination activity, it is essential to preserve the microbial community structure (bacterial and archaeal members) of this culture and supply an electron donor that produces high amounts of hydrogen when fermented. The study provides important information for the management of cultures to be used in bioremediation of TBBPA contaminated sites.