Cross-linked β-Mannanase Aggregates: Preparation, Characterization, and Application for Producing Partially Hydrolyzed Guar Gum.

β-Mannanase capable of hydrolyzing β-1,4-linkages in guar gum was immobilized as cross-linked enzyme aggregates (M-CLEAs). The aggregation and cross-linking process was optimized by response surface methodology (RSM) for maximum activity. The resulting M-CLEAs were characterized by FTIR, DSC, SEM, and SDS-PAGE. The M-CLEAs showed higher pH stability, improved thermal and storage stability, and reusability than free β-mannanase. For example, M-CLEAs were stable over broader pH range (5.5-8.5) with highest relative of activity of 98.17% at pH 6.5 and retained almost double activity than free mannanase at 50 °C after 4 h. Moreover, Km and Vmax of M-CLEAs were altered significantly, with a 1.5-fold increase and 0.98-fold decrease, respectively, than free β-mannanase. The prepared M-CLEAs could hydrolyze native guar gum (MW = 588,147 Da) to yield partially hydrolyzed guar gum (PHGG) (MW = 8023 Da).