Microbial reduction of manganese coupled to toluene oxidation

Toluene degradation occurred in anaerobic flow-through sediment columns filled with contaminated sediment and sludge to which either amorphous or highly crystalline manganese oxide was added. An enrichment culture from these sediment columns was able to grow on toluene under strictly anaerobic conditions in the presence of manganese oxide. The oxidation of toluene was coupled to the production of CO2 and to the reduction of Mn(IV). Of the different manganese oxides tested, the rate was slowest with crystalline manganese oxide. After several transfers of the enrichment culture, its ability to degrade toluene became less and it was ultimately lost, unless sterilized Rhine river sediment was present in the medium. Direct contact between the bacteria and the manganese oxide was found to be advantageous for a rapid toluene degradation. The degradation rate could be further increased by adding organic ligands such as oxalic acid or nitrilotriacetic acid.