Comparison of ionic liquids for efficient pretreatment of brewery spent grain

Abstract

A newly isolated fungus Aspergillus niger RCKH-3 was employed for cost effective production of a complete cellulase system under solid state fermentation (SSF). Overall evaluation criteria approach (OEC) was used as a novel approach for medium engineering to maximize the cellulase production. Among several factors studied, NH4Cl, inoculum age and temperature contributed maximally towards cellulase production. The highest interactions were observed between inoculum age and beef extract, followed by substrate to moisture ratio and PEG 8000. The statistical model provided optimal enzyme production conditions as: 5 g wheat bran; mineral salt solution (pH 5) and containing (g/L); NH4Cl (0.5), beef extract (2.0) and PEG 8000 (3.0) substrate to moisture ratio of 1:3.5 and 30% (v/w) 18 h old inoculum. Under optimum conditions, cellulase production experienced 2.5, 3.0 and 1.5 fold enhancements in FPase, CMCase and β-glucosidase activities, respectively. The estimated production costs ($ per 1000 units) for FPase, CMCase, β-glucosidase were 0.47, 0.21 and 0.04, respectively. Saccharification of office waste paper using crude cellulase resulted in reducing sugar yield of 534 mg/g dry substrate. Cellulase of newly isolated fungi A. niger RCKH-3 shows potential in biofuel applications based on its comparatively higher saccharification abilities and lower production costs.