Fermentative Production of Naringinase from Aspergillus niger van Tieghem MTCC 2425 Using Citrus Wastes: Process Optimization, Partial Purification, and Characterization.

Enzymatic hydrolysis of naringin by the action of naringinase is one of the standard practices adopted in the citrus fruit juice industry for debittering. In the present study, a submerged fermentation condition was optimized for producing naringinase from Aspergillus niger van Tieghem MTCC 2425. As per Placket-Burman design, pH (3-5), incubation temperature (26-30 °C), and inducer concentration (12-18 g·L-1) were the most important factors influencing the naringinase production. Naringin from citrus waste was used as an inducer. A rotatable central composite design was employed on these three variables and the numerical optimization predicted that fermentation at 29.8 °C, pH 4.7, and inducer concentration of 14.9 g L-1 would yield a maximum naringinase activity of 545.2 IU g-1. During partial purification, ion exchange chromatography led to a 9.92-fold increase in enzyme activity resulting a specific activity of 5460 IU g-1 with an activity recovery of 17%. As reflected by SDS-PAGE profile, the partially purified naringinase showed the molecular weight bands of 10-20, 65, and 80 kDa, respectively. The purified form of enzyme showed optimum stability at pH 5 and 50 °C. The naringinase activity was completely retained up to 150 days when stored at 4 °C.