Product inhibition of the fermentative formation of glutamic acid.

The addition of penicillin to cells of Corynebacterium glutamicum growing in 5-liter fermentors initiated the excretion of glutamic acid. The rate of glutamate production in fermentors declined continuously with time and reached 75% of the initial rate in 24 hr after penicillin had been added. The addition of glutamate to resting cell suspensions had only a slight effect on sugar utilization but caused a marked decrease in glutamate excretion. It is suggested that the high level of glutamate accumulating in the fermentation broth is responsible for inhibiting its own production.

Glucose-6-phosphate dehydrogenase and its deficiency in mutants of Corynebacterium glutamicum.

Corynebacterium glutamicum is a member of a group of taxonomically related glutamate-excreting bacteria which utilize glucose both by the Embden-Meyerhof and the pentose phosphate pathways, the latter sequence accounting for 10 to 38% of the glucose metabolized. Some of the properties of glucose-6-phosphate dehydrogenase in crude extracts of C. glutamicum were studied. The enzyme was rapidly inactivated by dilution in tris (hydroxymethyl)aminomethane-hydrochloride buffer. This inactivation was prevented by the presence of 0.45 m NaCl. Mg(++) was required for enzyme activity, but Mn(++), Ca(++), Sr(++), and Ba(++) were equally effective. Growth of the organism under differing conditions did not markedly affect the specific activity of the enzyme. A generally applicable method for detecting colonies deficient in glucose-6-phosphate dehydrogenase was developed. Mutants so obtained were found to be auxotrophic for tryptophan. Upon reversion of the tryptophan requirement, the revertants still retained the property of glucose-6-phosphate dehydrogenase deficiency. Neither the mutants nor the revertants could grow as rapidly as the parent culture in glucose, in gluconate, or in a complex medium.