Sulfate utilization by penicillin-producing mutants of Penicillium chrysogenum.

A great deal of work has been directed toward increasing the yield of penicillin in fermentations with Penicillium chrysogenum. The spectacular increase in yield which has been achieved has resulted, in the main, from two approaches. In the first approach, mutant strains of P. chrysogenum produced by spontaneous variation or by the action of mutagenic agents such as nitrogen mustard or ultraviolet light were selected for enhanced penicillin production. The development of the "Wisconsin family" of high yielding mutant strains of P. chrysogenum strain NRRL1951-B25 has been described by Backus and Stauffer (1955). Further enhancement of the yield of penicillin has resulted from a more complete definition of the environmental conditions (pH, temperature, constituents of the medium) necessary for the excretion of penicillin by the mold (Johnson, 1952). However, changes in the sulfur metabolism which accompany an increase in penicillin synthesis brought about either by mutation of the mold or by changes in the conditions of the fermentation, have not been investigated. It is the purpose of this paper to report differences in the utilization of sulfate and the excretion of sulfur compounds by various strains of P. chrysogenum when grown on a chemically defined medium with inorganic sulfate as the sole source of sulfur, with and without precursor addition, and to relate these differences with the capacity of the strain to synthesize penicillin. The strains of P. chrysogenum which were used in these experiments are listed in table 1.