β-Lactam production by a high producer,Cephalosporium acremoniumC-10, was reduced by high concentrations of phosphate (100 mM to 215 mM). The optimal concentration for antibiotic production by this strain was 25 mM. High concentrations of phosphate did not act by increasing the rate of glucose assimilation as previously concluded (Küenzi 1980). The three β-lactam synthetases tested, i.e., δ-(l-α-aminoadipyl)-l-cysteinyl-d-valine synthetase, cyclase and expandase, were all subject to phosphate repression as well as inhibition. The most susceptible to both kinds of regulation was the expan
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