Bacterial-assisted optimization of hydrolytic enzyme production from grape (vitis vinifera) pomace by solid-state fermentation.

The valorization of agro-industrial waste through solid-state fermentation (SSF) provides a sustainable strategy for waste conversion and enzyme production. This study aimed to optimize the concomitant production of a hydrolytic enzyme cocktail (pectinase, xylanase and amylase) by Bacillus subtilis 5140 (VKPM: B-1326) using red grape pomace as the sole substrate under SSF conditions. A, D-optimal response surface methodology (RSM) with a quadratic model was used to evaluate and optimize four process parameters: temperature (36-40 °C), pH (6-8), moisture content (60-70%), and incubation time (48-120 h), with the three enzyme activities considered jointly as responses. The statistical analysis showed that the quadratic model was significant for pectinase (R² = 0.9651) and xylanase (R² = 0.9784), whereas a two-factor interaction (2FI) model provided the best fit for amylase production (R² = 0.9659). The RSM optimization identified approximately 39 °C, pH 6.35, 65% moisture, and 57 h as the conditions for concomitant efficient enzyme production. Under these conditions, the model predicted activities of 402.82 U/g dry substrate (DS) for pectinase, 301.53 U/g DS for xylanase, and 112.43 U/g DS for amylase. The results indicate that D-optimal RSM could be used to identify similar fermentation conditions for simultaneous production of the three hydrolytic enzymes from grape pomace by SSF.