Benzoate degradation via the ortho pathway in Alcaligenes eutrophus is perturbed by succinate

Abstract

During batch growth of Alcaligenes eutrophus on benzoate-plus-succinate mixtures, substrates were simultaneously metabolized, leading to a higher specific growth rate (μ = 0.56 h-1) than when a single substrate was used (μ = 0.51 h-1 for benzoate alone and 0.44 h-1 for succinate alone), without adversely affecting the growth yield (0.57 Cmol/Cmol). Flux distribution analysis revealed that succinate dehydrogenase most probably controls the rate of total succinate consumption (the maximum flux being 9.7 mmol · g-1 · h-1). It is postulated that the relative consumption rate of each substrate is in part related to modified levels of gene expression but to a large extent is dependent upon the presence of succinate, end product of the β-ketoadipate pathway. Indeed, the in vitro β-ketoadipate- succinyl coenzyme A transferase activity was seen to be inhibited by succinate, a coproduct of the reaction.