EXTRACELLULAR PROTEASE PRODUCTION BY SUBMERGED CULTURES OF SCHIZOPHYLLUM-COMMUNE

Fungi live by secretion of hydrolytic enzymes into the growth substrat e and subsequent absorption of the products of hydrolysis by the mycel ium. We have investigated protease secretion by the wood-decaying basi diomycete, Schizophyllum commune, when grown submerged in a liquid min imal medium containing L-asparagine as the sole nitrogen source and in minimal medium supplemented with gelatin. The mycelia showed similar growth kinetics in both media; however growth rates were slightly high er in the gelatin-supplemented medium. The fungus lowered the pH of bo th media by nearly one unit over the course of 148 h of growth and sec reted measurable amounts of protein by 60 h. Proteases accumulated in both media; however, inclusion of gelatin resulted in substantially hi gher activity. These enzymes consisted almost entirely of serine and m etallo-endoproteases and at least one diaminodipeptidase. The proporti on of activity in each class, plus the absence in the medium of severa l mycelial proteolytic enzymes, suggests important differences in the mycelial and extracellular proteolytic systems. Gelatin-containing SDS PAGE also indicated differences in the mycelial and extracellular sys tems, with the extracellular system devoid of one of the major mycelia l proteases involved in autolysis, S. commune Protease B-designated Sc PrB. The mycelial aminopeptidase, APF, was not found in the medium, al though the mycelium produced a considerable amount of this activity. T hus, these extracellular activities are likely to be secreted and not simply the result of cell breakage.