BENZOATE DEGRADATION VIA THE ORTHO PATHWAY IN ALCALIGENES-EUTROPHUS IS PERTURBED BY SUCCINATE

During batch growth of Alcaligenes eutrophus on benzoate-plus-succinat e mixtures, substrates were simultaneously metabolized, leading to a h igher specific growth rate (mu = 0.56 h(-1)) than when a single substr ate was used (mu = 0.51 h(-1) for benzoate alone and 0.44 h(-1) for su ccinate alone), without adversely affecting the growth yield (0.57 Cmo l/Cmol), Flux distribution analysis revealed that succinate dehydrogen ase most probably controls the rate of total succinate consumption (th e 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 modi fied levels of gene expression but to a large extent is dependent upon the presence of succinate, end product of the beta-ketoadipate pathwa y, Indeed, the in vitro beta-ketoadipate-succinyl coenzyme A transfera se activity was seen to be inhibited by succinate, a coproduct of the reaction.