A Magnetic Bimodal Mesoporous Silica Biocatalyst via Cellulase Immobilization for Sustainable Production of Chitosan Oligosaccharides

Chitosan oligosaccharides (COS) are bioactive compounds with promising applications in functional foods, but their enzymatic production is hindered by high costs and operational instability. To address this, we developed a food-compliant magnetic bimodal mesoporous silica (Fe 3 O 4 @BMS) biocatalyst for sustainable COS synthesis via cellulase immobilization. The hierarchically structured carrier combined small (2–5 nm) and large (20–40 nm) mesopores, offering a large surface area of 851 m 2 /g. The immobilized cellulase demonstrated superior stability, maintaining 83.60 ± 3.32% residual activity at 80 °C, alongside exceptional pH adaptability (3–9). Magnetic Fe 3 O 4 integration facilitated rapid biocatalyst recovery, retaining about 70% of catalytic efficiency after 10 repeated cycles. In a scaled-up stirred-tank reactor, the system achieved a high yield of 316.33 ± 9.39 mg/g reducing sugar from chitosan after 5 h under optimized conditions. This work offers an industrially scalable route for COS production, aligning with green chemistry and food safety standards.