Stabilization of β-Galactosidase (from Peas) by Immobilization onto Amberlite MB-150 Beads and Its Application in Lactose Hydrolysis

The soluble PsBGAL (from Pisum sativum) is extremely unstable with loss of over 80% in enzyme activity within 24 h at 4 degrees C when the protein concentration was lower than 0.1 mg/mL. Enzyme immobilization onto Amberlite MB-150 beads (diameter = 5 mu m) greatly stabilized the enzyme preparation, with almost no loss for 12 months at room temperature (27 degrees C). Enzyme (21.9 mu g) was immobilized by 62.56% onto activated 100 mg of Amberlite MB-150 beads using 4% glutaraldehyde, at pH 6.0 (50 mM, sodium phosphate buffer). Statistical analysis carried out by ANOVA revealed that all parameters used during immobilization were equally important at P < 0.05 (level of significance). An approach toward commercial exploitation of Amberlite-PsBGAL especially in lactose hydrolysis was anticipated due to improved physicochemical properties including broad optimum pH and temperature, with a K-m of 4.11 +/- 0.21 mM for lactose. Amberlite-PsBGAL hydrolyzed 64.57 and 69.18% of lactose present in milk and milk whey, respectively, within 10 h (at room temperature). Immobilized enzyme has reusability of over 10 batchwise uses, with almost no loss in activity. The easy accessibility of enzyme source, ease of its immobilization on Amberlite, lower cost of Amberlite, enhanced stability of Amberlite-PsBGAL, and comparable lactose hydrolysis in milk and milk whey described here make it a suitable product for future applications at laboratory and industrial scale.