Development of Magnetic Immobilized Cellulase Biocatalysts for Saccharification of Paper Waste

Abstract

Saccharification of cellulosic material is crucial before utilizing it as the feedstock of fermentation processes. This study focuses on developing of robust catalysts for enzymatic hydrolysis of paper waste. Cellulase enzyme was immobilized on Fe₃O₄ magnetic nanoparticles (MNPs) via multi-covalent bonds. Therefore, the attachments of MNPs were performed by three approaches (3-aminopropyl)triethoxysilane (APTES) (Method I), polyethyleneimine (PEI) (Method II), and both monolayer molybdenum disulfide and PEI (MoS₂-PEI) (Method III). The biocatalysts were characterized using Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA). The immobilization yield and loading efficiency of cellulase were determined at 38.65% and 162 mg g⁻¹ in Method I, 13.33% and 31 mg g⁻¹ in Method II, and 14.38% and 33 mg g⁻¹ in Method III. The specification of the biocatalysts was determined for the hydrolysis of filter paper, carboxymethylcellulose (CMC), microcrystalline cellulose, and cellobiose. The total cellulase activity was 2.77, 0.943, 1.38, and 2.02 µmol_Glucose mg_Enzyme⁻¹ h⁻¹for free-cellulase and the immobilized biocatalysts prepared by Method I, II, and III, respectively. The prepared biocatalyst in Method I maintained 54.54% of its original activity after five cycles, which was more robust than Method II (20.25%) and Method III (12.33%). Further studies were performed on the saccharification of paper waste. The results showed the biocatalyst obtained by Method II resulted in 5.8 folds of higher glucose than the free-cellulase. The highest glucose recovery of about 72.47% was achieved after 48 h using the immobilized biocatalyst prepared by Method II.

Graphical Abstract