Immobilization of crude cellulase from Aspergillus foetidus on agar xerogel and its application for carrot juice extraction.

Abstract

This study investigates the immobilization of crude cellulase from Aspergillus foetidus, produced through solid-state fermentation by different methods, including entrapment in agar cube, adsorption on agar xerogel, and adsorption on agar xerogel pretreated with glutaraldehyde. The immobilization efficiency achieved was 90.80%, 84.08%, and 84.23%, while enzyme activity obtained was 1.12 IU/g, 1.52 IU/g, and 1.48 IU/g for crude cellulase immobilized by entrapment in agar cube, adsorption on agar xerogel, and adsorption on agar xerogel pretreated with glutaraldehyde respectively. The immobilized crude cellulase was characterized, revealing an optimal temperature shift from 50 °C to 60 °C for agar xerogel-adsorbed crude cellulase, which improved its thermal stability. The pH optimum for free and all immobilized crude cellulase was observed at pH 4. Also, all immobilized crude cellulases retained significant activity even after multiple cycles, depicting their reusability. The enzyme kinetics observed were K_m of 11.71 mg/mL, 57.0 mg/mL, 14.86 mg/mL, 62.32 mg/mL, while V_max was 4.20 µmol/mL/min, 6.58 µmol/mL/min, 3.25 µmol/mL/min, and 5.78 µmol/mL/min for free crude cellulase, crude cellulase immobilized by entrapment in agar cube, crude cellulase adsorbed on agar xerogel, and crude cellulase adsorbed on agar xerogel pretreated with glutaraldehyde respectively. The free and immobilized crude cellulases were applied for carrot juice extraction which showed increased juice yield, clarity, and reducing sugar content while reduced viscosity compared to untreated samples. These findings highlight agar xerogel as an encouraging support for cellulase immobilization, presenting a sustainable and economical method for enzyme reuse in food processing.