Phytase of Molds Used in Oriental Food Fermentation

Molds commonly used in Oriental food fermentation have been examined for their ability to produce phytase. Except for Mucor dispersus NRRL 3103 and Actinomucor elegans NRRL 3104, all the other molds tested produced both extra‐ and intracellular phytase. The enzyme produced by Aspergillus oryzae NRRL 1988 was purified by acetone fractionation, gel filtration, and diethylaminoethyl‐cellulose chromatography. The phytase was successfully separated from an acid phosphatase, and a 44‐fold increase in specific activity was observed. The pH optimum of 5.3 characterizes the enzyme as an acid phosphohydrolase, and its maximum activity at 50°C suggests a relatively high thermostability. The enzyme is also fairly stable over a pH range 3.5‐7.8 at 25°C. The A. oryzae phytase is active with either phytic acid or glycerophosphate. as substrate, but it hydrolyzes phytic acid twice as fast as it does glycerophosphate. However, the enzyme is partially inhibited by high concentration of phytic acid. The Km value of A. oryzae phytase was estimated as 0.47 mM and V max was 11.9 μmoles P i per mg per mg protein.