Sulfur metabolism of a mutant of Cephalosporium acremonium with enhanced potential to utilize sulfate for cephalosporin C production.

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Abstract
Characteristics of a mutant of C. acremonium with enhanced potential to utilize sulfate for cephalosporin C production were investigated with S-starved cells. DL-Norleucine showed an inhibitory effect on cephalosporin C and penicillin N production by the mutant in the presence of a S source such as sulfate, sulfite, thiosulfate and L-cystine, but it exhibited no effect when it was added after a certain period of incubation. Antibiotic production by the parent was stimulated by norleucine regardless of the addition time. An increase in the intracellular cysteine pool was found when the cells were incubated with L-methionine or norleucine and sulfate. Enzymatic studies revealed that methionine and norleucine stimulated the cysteine desulfhydrase formation, and this effect was significant in the mutant. The mutant had an enhanced L-serine sulfhydrylase activity. The increase in this enzyme activity in the mutant seems responsible for the increase in the sulfate-utilizing ability and the methionine sensitivity by maintaining a high level of the cysteine pool. The effect of methionine and norleucine is assumed to be exerted through cysteine.