The present study was designed to produce phytase by screening the isolated strains of indigenous fungi and their substrates. It was performed on 6 substrates to find the higher activity of phytase which was obtained from 11 fungal isolates. A highly phytase producing strain was screened along with substrate; furthermore, the isolated strain was identified as Aspergillus terreus (OP028905) by 18SrRNA gene sequencing. Wheat bran was selected as a substrate using the One Variable at a Time (OVAT) strategy. Physico-chemical parameters were optimized through statistical designs, Response Surface Methodology (RSM) and Taguchi in solid-state fermentation. Central Composite Design (CCD) was selected through RSM and applied to analyze the relationship between the tested variables (temperature, pH, time period, inoculum size, moisture content, substrate concentration, and nitrogen source). RSM phase-I exhibited 192 IU/mL; phase-II exhibited 245 IU/mL, while Taguchi method showed 155 IU/mL as maximum activity. RSM exhibited 36% more phytase production than Taguchi method. Among these designs RSM phase-II exhibited maximum activity. Conclusively, the optimized conditions based on RSM came out as temperature 50˚C, pH 8.0, inoculum size 2mL, time period 1 day, moisture content 60%, substrate concentration 10g, and nitrogen source (0.2mg).

Keywords: fungal isolates, RSM, Taguchi, solid-state fermentation