Short-Term Glucose Release from Ultrasound-Assisted Alkali-Pretreated Hemp Hurds Using Free and Magnetic Nanoparticle-Immobilised Cellulase

The enzymatic conversion of lignocellulosic biomass (LB) into fermentable sugars is important for the development of sustainable biorefineries. This study investigated the immobilisation of Trichoderma reesei (T. reesei) cellulase on amine-functionalised magnetic nanoparticles (MNPs) and evaluated the resulting biocatalyst for the hydrolysis of pretreated hemp hurd (HH) biomass. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) provided evidence consistent with cellulase association with the nanoparticles, with the estimated dry-state particle diameter increasing from 22.4 ± 0.4 to 27.8 ± 0.3 nm after immobilisation. The selected immobilised catalyst loading produced approximately 89% of the total filter-paper assay response obtained with the selected free-enzyme loading, although this comparison was not normalised to protein content. During 7 h hydrolysis experiments, glucose production increased progressively for both enzyme forms. Across the tested enzyme dilutions, immobilised cellulase generated approximately 88–91% of the glucose produced by free cellulase. The immobilised enzyme also retained approximately 64% of its initial hydrolysis performance after five reuse cycles. These findings demonstrate the potential of magnetic cellulase nanobiocatalysts for recoverable and reusable hydrolysis of lignocellulosic biomass. However, further studies are required to determine protein-normalised activity, immobilisation efficiency, longer-term stability, process economics and industrial scalability.