Enhancing the Catalytic Performance of β-Mannanase via Polyvinyl Alcohol Immobilization and Genipin Modification

This study reports the immobilization of β-mannanase from <i>Aspergillus niger</i>-either unmodified or genipin-modified-within polyvinyl alcohol hydrogels (PVA@mannanase and PVA@mannanase-Gen) for the enhanced production of mannooligosaccharides (MOSs). All enzyme preparations showed an optimal pH of 5.0, while immobilization shifted the optimal temperature from 40 °C for the free enzyme to 55 °C for the immobilized forms. Genipin modification notably improved stability, increasing the half-life from 25.3 h (free enzyme) to 429.2 h in PVA@mannanase-Gen, and raised catalytic efficiency by approximately 2.3-fold. Both immobilized preparations retained over 75% of their activity after five reuse cycles at pH 5 and 55 °C. Using PVA@mannanase-Gen under these optimized conditions, MOSs were effectively produced, with mannotetraose as the predominant product. To explore their potential applications, the MOSs generated from locust bean gum were evaluated for effects on MCF-7 and HCT-116 cancer cell lines, resulting in moderate growth inhibition (~24-25% at 0.4 mM after 24 h). Together, these findings demonstrate that the immobilization of the genipin-modified enzyme not only enhances β-mannanase stability and performance but also supports the efficient production of MOSs with promising antitumoral activity.