Bone-bound enzymes for food industry application

The immobilisation of beta-galactosidase and amyloglucosidase (AMG) by means of physical adsorption on to bone powder is described. The influence of the enzyme load, applied to the support on immobilisation, yield and efficiency, has been determined. The immobilisation process improved the thermal stability of beta-galactosidase (at 37 degrees C), while immobilised AMG displayed a stability (at 55 degrees C) similar to that of the soluble enzyme. The apparent K-M (K-app) values have been determined for both derivatives, for the beta-galactosidase derivative K-M was 3 mM using the artificial substrate ONPG and, for the AMG derivative, it was 1 mg/ml using soluble starch as substrate. The extent of lactose hydrolysis achieved, batchwise, with beta-galactosidase derivatives acting on lactose buffered solutions, whey, whey permeates and skimmed milk, was in the range of 90% and decreased to 50% after 3 reuses. The conversion of 30% (w/v) liquefied cassava starch achieved with the AMG derivative was 98% until the 11th reuse, and over 95% until the 20th reuse. (C) 2000 Elsevier Science Ltd. All rights reserved.