The use of chemical uncouplers for reducing biomass production during biodegradation

Reducing the energy available for anabolism of cell mass was identified as a method to minimise disposal requirements of excess biomass produced in the activated sludge process. A model system consisting of Pseudomonas putida, maintained in a chemostat, was employed to investigate biomass production in the presence of the energy dissipating protonphore, p-nitrophenol (pNP). The efficiency of biomass production was reduced by up to 62% when the feed was supplemented with 100 mg pNP.l(-1) with a simultaneous increase in the specific substrate uptake rate. The data obtained have been analysed to reveal maintenance energy requirements and true growth yields. Cells were found to satisfy their maintenance energy requirements prior to utilising energy in anabolism. Decreases in pH alone had no effect on biomass production, but caused additional protonphore induced reduction of biomass production. A pH 6.2 the efficiency of biomass production was reduced by up to 77% when the feed was supplemented with 100 mg pNP.l(-1). (C) 1998 IAWQ. Published by Elsevier Science Ltd.