Corn (Zea Mays) Leaves as Cost-Effective Substrate for Enhanced Tannase Production Under Solid State Fermentation: Optimization and Characterization

Abstract

The current study reports the utilization of agricultural residues of corn (Zea mays) as lower-cost substrate for the production of tannase under solid state fermentation (SSF). Tannase producing bacterial strains were isolated from gut content of freshwater fish, Ctenopharyngodon idella, and highest tannase producer was identified as Bacillus cereus using 16S rDNA sequencing. For enhanced tannase production, B. cereus was investigated using one variable at a time (OVAT) followed by central composite design (CCD) of response surface methodology (RSM). Under OVAT, optimal fermentation conditions and medium composition were achieved with 70% substrate moisture, distilled water (1 ml) as enzyme extraction medium, 30°C incubation temperature, 3.0 pH, 1% inoculum size, 24 h incubation time, 150 rpm agitation, large-sized substrate particles (4 mm), non-centrifugation condition, NaCl salt, 1.5% tannic acid substrate and malt extract as organic nitrogen source for maximal enzyme synthesis. The highest tannase was produced (155.74±1.67 U/ml) with 1.75% tannic acid, 0.75% NaCl and 1.25% malt extract with the application of CCD of RSM. Higher coefficient of regression (R2=0.9665) indicated that second-order polynomial regression model assessed the data excellently. Further, tannase characterization depicted its maximum activity at 5.0 pH, 50°C temperature, 45 min incubation and 0.35% tannic acid.