Characterization of extra- and intracellular phytases from Rhizopus oligosporus used in tempeh production.

Rhizopus oligosporus strain CT11K2, commonly used in tempeh (fermented soybean) production produced both extra- and intracellular phytases. The enzymes were isolated from growth media and the cultured mould and partially purified by acetone fractionation, gel filtration on Sephadex G-100 and DEAE-cellulose chromatography. Intracellular phytase activity was higher than that of the extracellular enzyme. Both enzymes showed maximum activity at pH 4.5 and 55 degrees C, suggesting relatively high thermostability. The enzymes were partially inhibited by high concentrations of substrate. The Km and Vmax values of the extracellular phytase were 0.15 mM and 0.076 mumol Pi per min per ml DEAE-cellulose purified enzyme, respectively, and for the intracellular phytase were 0.17 mM and 0.34 mumol Pi per min per ml enzyme, respectively. Extracellular phytases showed inactivation and activation energies for the hydrolysis of phytic acid of approximately 28,300 cal per mol and 6100 cal per mol, respectively, while inactivation and activation energies for the intracellular phytase were approximately 33,200 per mol and 9500 cal per mol, respectively.