Cell-free ring expansion of penicillin N to deacetoxycephalosporin C by Cephalosporium acremonium CW-19 and its mutants.

Abstract
To examine microbiological ring expansion of penicillin N to a cephalosporin, 5 mutants of C. acremonium blocked in .beta.-lactam antibiotic biosynthesis were obtained from 2500 survivors of mutagenesis. In submerged fermentation, mutants M-0198, M-0199 and M-2351 produced no .beta.-lactam antibiotic (type A), but mutants M-1443 and M-1836 formed penicillin N but not cephalosporin C (type B). Cell-free extracts of type A mutants converted penicillin N to a cephalosporin; those of type B mutants did not. The product of the cell-free reaction was identified as deacetoxycephalosporin C by TLC paper chromatography, paper electrophoresis and enzyme tests. Penicillin N is apparently an intermediate of cephalosporin biosynthesis.