Phytase production by the thermophilic fungus Rhizomucor pusillus

A thermophilic fungus, Rhizomucor pusillus, isolated from composting soil, was studied for phytase production using solid-state fermentation. The optimization of phytase production was carried out by Box–Behnken design of experiments, using three independent variables (pH of medium, culture age and incubation period), resulting in a maximal level of phytase (9.18 units/g substrate). The partially purified phytase was optimally active at 70 °C and pH 5.4, though the enzyme showed 80% activity over a wide pH range, 3.0–8.0. The phytase was found to have broad substrate specificity.