Optimization of naringinase production by Bacillus megaterium CP026736 under solid-state fermentation

Naringinase is an industrially important enzyme widely used in food, pharmaceutical, and biotechnological applications, particularly for citrus juice debittering. In the present study, naringinase production by Bacillus megaterium CP026736 was optimized under solid-state fermentation (SSF) using rice bran as a low-cost agro-industrial substrate. A one-factor-at-a-time (OFAT) approach was employed to evaluate the influence of physicochemical and nutritional parameters on enzyme production. Maximum naringinase activity (948.55 U/g) was achieved at 37 °C, pH 6.0, 6 days of fermentation, and an inoculum size of 1×10⁶ cells/mL. Optimum nutritional conditions included 10 g/L peptone, 4 g/L glucose, 4 g/L naringin, 0.6 g/L MgSO₄·7H₂O, 0.1 g/L KH₂PO₄, and 0.05 g/L each of ZnSO₄·7H₂O, CuSO₄·7H₂O, and FeSO₄·7H₂O. Rice bran at 30% (w/v) was identified as the most effective substrate concentration for enzyme production. Under optimized conditions, naringinase activity increased 1.73-fold from 547.34 U/g to 948.55 U/g. These findings demonstrate the potential of B. megaterium CP026736 as an efficient and cost-effective source for industrial naringinase production under SSF conditions.