HYDROLYSIS OF LACTOSE IN ACID WHEY USING β‐GALACTOSIDASE ADSORBED TO A PHENOL FORMALDEHYDE RESIN

Publisher Website
Google Scholar
Abstract
The feasibility of using immobilized enzymes for the commercial hydrolysis of lactose in acid whey was investigated. The areas of enzyme kinetics, enzyme adsorption, mass transfer, reactor design and economics were considered. All reaction studies were carried out at 40°C, pH 4. Adsorption of β‐galactosidase into a porous phenol formaldehyde resin (Duolite ES‐762) followed an S‐shaped isotherm at low concentrations and adsorption increased with temperature at 0, 24 and 26°C. Up to 0.6g of Wallerstein enzyme preparation (4043 activity units) were adsorbed to 1g of dry resin. Adsorption had little effect on enzyme activity. An integral reactor of immobilized β‐galactosidase retained nearly full activity for over 120 days of continual hydrolysis of lactose in acid whey and pure lactose solutions. Throughout the long term study, mold was effectively inhibited by the use of 0.1% w/v of potassium sorbate and CO2. Based on 120‐day catalyst life and the integral reactor data for Duolite ES‐762 loaded with 0.23g enzyme/g dry resin, the catalyst cost for the hydrolysis of 1 lb of lactose is 1.65 cents at 40% conversion using 50 mesh resin.