A number of Cephalosporium acremonium mutants blocked in the synthesis of cephalosporin C were investigated for accumulation of other ,3-lactam compounds. The non-cephalosporin C producers were isolated after exposing the superior cephalosporin C-producing strain M8650-4 to ultraviolet light (268 nm). One of the blocked mutants, MH63, accumulated deacetylcephalosporin C (0.4 mg/ml), deacetoxycephalosporin C (1.5 mg/ml), and penicillin N (2.7 mg/ml). In contrast, the parent of MH63 produced high levels of cephalosporin C as well as deacetylcephalosporin C (2.2 mg/nal) and penicillin N (1.0 mg/ml), but only traces of deacetoxycephalosporin C (about 0.1 mg/ml). Deacetoxycephalosporin C was isolated from the mutant strain and identified by ultraviolet light, nuclear magnetic resonance, bioactivity spectrum, and co-migration with authentic standard in three chromatography systems.

Homogeneous suspensions of streptomycete spores were desirable for plating after mutagenesis. Filtration through 8-μm membrane filters (Millipore Corp.) more effectively separated hyphae and spore clumps from single spores than did filtration through cotton wefts or paper.