Hydrolysis of lactose in acid whey using β‐galactosidase immobilized on porous glass particles: Preparation and characterization of a reusable catalyst for the production of low‐lactose dairy products

Partially purified lactoses (β‐D‐galactoside galactohydrolase, EC 3.2.1.23) from Aspergillus niger, Ladobacillus helveticus, and Saccharomyces lactis were immobilized on diazotized porous glass particles (mean pore diameter, 86.5 nm: particle size diameters, 75–125 μm). In acid whey containing 4–4.5% lactose, A. niger lactase gave the highest activity (89 μmoles lactose hydrolyzed/g glass, min) at 55°C and pH 4.5. Glass‐immobilized A. niger laclases (lactase‐BG) retained much hydrolytic activity after storage and periodic use for 165 days at 55°C. For values of X greater than 30%, hydrolysis of 0.12M lactose in acid whey by a continuous flow column packed with 2 ml of lactase‐BG particles could be correlated by X = 17.2(V/F) + 12.5 where X = lactose hydrolysis, percent of lactose originally present; V = volume of packed bed of lactase‐BG, ml; F = flow rate of acid whey, ml/min.