Statistical optimization and mutagenesis for high level of phytase production by Rhizopus oligosporus MTCC 556 under solid state fermentation.

The present study deals with production of phytase from Rhizopus oligosporus MTCC 556 by solid state fermentation (SSF) using different (ADT27, IR20, PAIYUR1, KG, and RASI) rice bran varieties, in which ADT27 rice bran yield maximum of 6.2 U gds⁻¹ phytase. Statistical optimization was employed by Central Composite Design (CCD); the results showed that 3.0 g dextrose, 2.5 g ammonium nitrate, substrate size of 80 mesh, 10 mg calcium chloride was 116 hr at optimal for phytase production by SSF, with maximum of 23.14 U gds'. Phytase production improved by 4 fold (31.3 U/gds) due to chemical mutagenesis (mutant Rhizopus oligosporus MTCC 1116) in optimized media composition. Partially purified phytase showed approximately 90 kDa of molecular mass and was optimally active at 5.5 pH and 50°C temperature. Substrate specificity exhibited in sodium phytic acid and phytase activity was stimulated by Zn²⁺ and Ca²⁺.