Effect of a mixed substrate on phytase production by Rhizopus oligosporus MTCC 556 using solid state fermentation and determination of dephytinization activities in food grains

Mustard oilcake was used as a novel substrate for phytase production with Rhizopus oligosporus MTCC 556. A mixed substrate (wheat bran:mustard oil cake) was used to optimize different medium components under solid state fermentation at a 62% moisture content, pH 5.5, 30°C, an inoculum level of 15%, and a ratio of the volume of a salt solution to the mass of mixed substrate 1.5 mL:10 g. Different carbon and nitrogen sources were used for production of phytase. Use of the nutritional supplements maltose and ammonium sulfate resulted in high phytase yields. The hydrolytic ability of partially purified phytase was evaluated using 5 different food grains. Wheat flour showed a 43.78% phytic acid reduction, rice flour showed 92% release of inorganic phosphorus, and corn flour showed 81 and 68% releases of soluble proteins and reducing sugars. Thus, phytase is suitable for feed applications.