Biodegradation of benzoate with nitrate as electron acceptor at different redox potentials in sand column microcosms

The purpose of this work was to assess the influence of redox conditions on benzoate biodegradation coupled with oxygen and nitrate as electron accepters. A benzoate-degrading, facultatively denitrifying bacterium was isolated from a sediment sample and was tentatively identified as Comamonas terrigena (strain J92-6). The experimental system was based on sand columns that were filled with liquid medium containing benzoate and nitrate. The columns were inoculated to provide a fixed biofilm on the sand, Conditions were created by aeration, dinitrogen-purging, and sodium sulfide amendment that comprised oxic, anoxic, and reduced (-375 mV) zones, respectively, at different depths of the columns, Anaerobic biodegradation of benzoate was nitrate-dependent and proceeded at all redox potential values ranging from +400 to -375 mV, Thus, benzoate degradation coupled with denitrification was not inhibited at low redox potentials characteristic of sulfate reduction and methanogenesis. The results demonstrate that the fixed biofilm column system can be successfully used to evaluate the influence of environmental factors on the biodegradation of benzoate, a central decomposition product of anaerobic, aromatic hydrocarbon biodegradation.