EFFECT OF WATER ACTIVITY ON PRODUCTION AND ACTIVITY OF RHIZOPUS-OLIGOSPORUS POLYSACCHARIDASES

During tempeh fermentation, Rhizopus oligosporus produced polysaccharidases to degrade soya bean cell walls; the maximum activity for all polysaccharidases tested occurred 20-30 h after inoculation. R. oligosporus was also grown in a soya bean extract model medium to which glycerol was added to control water activity (a(w)). The overall activities of the major enzymes produced by the fungus, polygalacturonase, endocellulase and xylanase, appeared to be strongly influenced by a(w). The production of enzymes as well as their specific activities were affected by a(w). The optimum a(w) for polygalacturonase and xylanase activity coincided with that for mycelial growth, namely 0.99-1.00. In contrast, the optimum a(w) for (endo)cellulase was 0.98, at which mycelial growth was significantly reduced.