Optimization of conditions for production of pectinase in solid-state fermentation with Aspergillus flavus using dried Assam lemon peel powder as substrate
Nurin Afzia, Nipona Shill, Bhaskar Jyoti Kalita, Nandan Sit
Abstract
The culture conditions for pectinase production with Aspergillus flavus by solid-state fermentation (SSF) using dried Assam lemon peel were optimized and the pectinase was used for clarification of grape juice. A central composite rotatable design (CCRD) was used for optimization experiments with moisture content (50-90%), incubation temperature (20-60 ℃), incubation time (96 h–192 h), and urea concentration (0–1%) as independent variables, and pectinase activity as dependent variable. The optimum conditions for pectinase production obtained were moisture content of 60%, incubation temperature of 50 ℃, incubation time of 96 h, and urea concentration of 0.30% with a pectinase activity of 3.68±0.20 U/mL where one unit of pectinase activity corresponds to number of µmole of galacturonic acid released in one minute in 1% pectin solution at 37°C and 4.8 pH. The crude pectinase was found to have maximum activity at a temperature of 40 ℃ and pH 4 and had an apparent Vmax and Km of 6.10 U/mL and 6.62 mg/mL respectively. The grape juice clarified using the crude pectinase showed decreased optical density (1.45±0.06 to 1.17±0.07) and viscosity (1.76±0.10 to 1.46±0.07 mPa.s) and increased reducing sugar content (13.90±0.10 to 16.96±0.06 g/100 mL juice), and total soluble solids (17.77±0.16 to 18.50±0.30 °Brix).