Cellulase Immobilization onto Magnetic Halloysite Nanotubes: Enhanced Enzyme Activity and Stability with High Cellulose Saccharification

A quest for efficient biotransformation of cellulosic material into sustainable biochemical products for recent biotechnological interventions is currently under way. Herein, we report the fabrication of nanobiocatalyst (NBC) employing halloysite nanotubes (HNTs) as a template for immobilizing cellulase enzyme, which catalyzed the hydrolysis of cellulose into glucose. Magnetic character was imported to HNTs by in situ anchoring of iron oxide nanoparticles, onto which cellulase was immobilized using aminosilane surface-functional chemistry. Characterization studies revealed nanobiocatalyst to be extremely stable during heterogeneous catalysis without compromising their catalytic activity. The optimization of process parameters yielded ∼93.5% activity of cellulase with high enzyme loading (111.6 mg·g–1 HNTs) after immobilization. Immobilized cellulase displayed superior stability at elevated temperatures (≥60°C) and storage capability compared with their free forms. The NBC even retained ∼68.2% of its original activity after seven consecutive uses with a minimum yield of 25.4 mg glucose·g–1 cellulose and was 100% recoverable using a magnet. Displaying a high ionic-liquid tolerance ability is concurrent with superior catalytic potential against CMC and extracted cellulose (bagasse), and achieving ∼50.2% saccharification and 0.56 g glucose·g–1 cellulose within 48 h of continuous operation establishes the commercial viability of using cellulase-immobilized HNTs for efficient cellulose hydrolysis. The sustainability and eco-friendly endeavors in this approach would pave the way toward valorization and consolidated bioprocessing of cellulose materials.