Metabolic uncouplers for controlling biomass accumulation in biological waste treatment systems

A number of lipophilic weak acids are known to reduce biomass production in biological waste treatment systems. A definitive mechanism on how metabolic uncouplers reduce biomass accumulation is yet to be developed. In addition to the classic uncoupler mechanism of reduced ATP production efficiency, three other mechanisms are reviewed here. Firstly, uncouplers can increase maintenance energy requirements by diverting energy to non-growth processes. Secondly, uncouplers can undermine biofilm integrity through changes in EPS production, quorum signaling molecules, and potentially, cell hydrophobicity. Finally, uncoupler toxicity can challenge the microbial diversity, leading to death of some and proliferation of new species in the biofilm with reduced biomass yield. There are observations linking these mechanisms together but more work is required to clarify them. Given the challenges of acclimation, accumulation and environmental risks associated with uncouplers, understanding how these mechanisms operate is imperative in their successful and sound application.