Immobilization of indigenous holocellulase on iron oxide (Fe2O3) nanoparticles enhanced hydrolysis of alkali pretreated paddy straw

•Holocellulase from Aspergillus niger SH3 was characterized using LC-MALDI MS/MS.•Total of 125 proteins including cellulases, xylanases and esterases were identified.•Fe2O3 covalently immobilized enzyme showed better immobilization efficiency.•Immobilized enzyme showed higher Vmax and lower Km than free enzyme.•Fe2O3 immobilized enzyme gave 10 % higher saccharification yield then free enzyme. The holocellulase from Aspergillus niger SH3 was characterized and found to contain 125 proteins including cellulases (26), hemicellulases (21), chitinases (10), esterases (6), amylases (4) and hypothetical protein (32). The crude enzyme was immobilized on five different nanoparticles (NPs) via physical adsorption and covalent coupling methods. The enzyme-nanoparticle complexes (ENC) were screened for protein binding, enzymatic activities and immobilization efficiency. Magnetic enzyme-nanoparticle complexes (MENC) showed higher immobilization efficiency (60–80%) for most of the enzymes. MENC also showed better catalytic efficiencies in term of higher Vmax and lower Km than free enzyme. Saccharification yields from alkali treated paddy straw were higher (375.39mg/gds) for covalently immobilized MENC than free enzyme (339.99mg/gds). The immobilized enzyme was used for two cycles of saccharification with 55% enzyme recovery. Hence, this study for the first time demonstrated the immobilization of indigenous enzyme and its utilization for saccharification of paddy straw.