Further studies on the bioconversion of penicillin G into deacetoxycephalosporin G by resting cells of Streptomyces clavuligerus NP-1

Resting cells of Streptomyces clavuligerus NP-1, which possess deacetoxycep halosporin C synthase activity, have been shown previously to perform oxida tive ring expansion of penicillin G in the presence of iron, ascorbic acid, and cr-ketoglutaric acid to form deacetoxycephalosporin G. Further studies on this bioconversion indicated that use of MOPS or HEPES buffer at pH 6.5 more than doubled the extent of the reaction observed With the previously used Tris-HCl at pH 7.4. Levels of bioconversion as high as 16.5% were achi eved at low penicillin G concentrations. Previously, conversion yields were <1%.