Low energy gain from formate oxidation during bacterial growth on 2,4‐dichlorophenoxyacetic acid

Abstract Alcaligenes eutrophus JMP 134 was chemostatically grown on 2,4‐dichlorophenoxyacetic acid (2,4‐D) at a dilution rate of 0.06 h−1; formate was fed as an auxiliary energy source. The simultaneous utilization of both components resulted in an increase in growth yield. As an example, this figure increased from 0.18 g dry mass/g 2,4‐D to 0.25 g dry mass/g 2,4‐D during growth on 1 g/l 2,4‐D plus 3 g/l sodium formate. The increase was correlated to energy generated from formate oxidation. Accordingly, a P/O‐quotient of 1 was derived for the energy transduction of NADH obtained from formate oxidation as it was for the overall efficiency during growth on 2,4‐D itself. This low energy yield was attributed to uncoupling exerted by 2,4‐D. The theoretical maximum yield coefficient of 0.69 g/g could not be reached due to the limiting activity of formate dehydrogenase in the conversion of the required quantities of formate.