Use of chickpea (Cicer arietinum L.) milling agrowaste for the production of tannase using co-cultures of Aspergillus awamori MTCC 9299 and Aspergillus heteromorphus MTCC 8818

Response surface methodology (RSM) was applied to optimize tannase and gallic acid production by co-cultures of Aspergillus awamori MTCC 9299 and Aspergillus heteromorphus MTCC 8818 under solid state fermentation of chickpea seed coat—a major byproduct of the chickpea milling industry rich in phenolic compounds, especially tannins. A Box-Behnken design using RSM with four variables, namely pH, temperature, incubation period, and moisture level, was used to optimize significant correlation between the effects of these variables on tannase, gallic acid and residual tannic acid. Maximum response was predicted to be 7.3 ± 0.4 U/g dry substrate (ds) tannase, 9.3 ± 0.46 mg/mL gallic acid production and 3.3 ± 1.1 mg/mL residual tannic acid under optimized conditions of pH 4.5, temperature 29.7 °C, 126.3 h incubation period and 113.9 % moisture level with a calculated desirability of 0.77. Experimental values were in good agreement with predicted values, and the models were highly significant, the correlation coefficient (R 2) being 0.76, 0.88 and 0.72 for tannase, gallic acid and residual tannic acid, respectively.