Effect of chemical uncoupler on the observed growth yield in batch culture of activated sludge

Microbial metabolism is the sum of biochemical transformation that includes interrelated catabolic and anabolic reactions. It has been demonstrated that coupling between anabolism and catabolism can be seriously dissociated by chemical uncoupler. Based on the knowledge on energy uncoupling resulting from substrate excess, a growth yield model was developed for chemical uncoupler-containing batch culture of activated sludge, and was verified with experimental and literature data. The observed growth yield was found to decrease with increasing the ratio of initial uncoupler concentration to initial biomass concentration (Cu/Xo), which represents the real strength of chemical uncoupler exerted on unit biomass. The presence of chemical uncoupler in the culture medium can cause significant energy spilling. It appears that energy spilling may be an effective pathway for bacteria to protect themselves against abnormal living conditions, but at the cost of consuming nongrowth energy.