Fermentative Production of Naringinase from Aspergillus niger van Tieghem MTCC 2425 Using Citrus Wastes: Process...

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.