Performance of lactase encapsulated in pectin-based hydrogels during lactose hydrolysis reactions

Abstract

The aim of this work was to evaluate the performance of lactase encapsulated in pectin-based hydrogels during lactose hydrolysis reactions. Pectin-based hydrogel and pectin-based composite hydrogel containing pine fiber were synthesized by chemical cross-linking. Lactase was encapsulated in both hydrogels by adsorption. Lactose hydrolysis experiments were conducted by immersing encapsulated lactase in standard lactose solutions, varying pH and temperature. The formed glucose concentrations were determined by UV–vis spectrophotometry, using an enzymatic-colorimetric method. The lactase encapsulation, catalytic activity, lactose hydrolysis and lactase release were affected by the drying of the hydrogel (oven or freeze-drying), pH and temperature variation of the aqueous lactose solution and pine fiber content in the polymer network. The encapsulation efficiencies of lyophilized hydrogels containing 0, 5 and 10% of pine fiber were 69.04 ± 1.19, 69.57 ± 0.78 and 71.10 ± 0.35%, respectively. Slightly lower values were found for air-dried hydrogels. The relative catalytic activities of lactase encapsulated in the hydrogels containing 0, 5 and 10% of pine fiber were, respectively, 52.85 ± 0.97, 56.26 ± 1.07 and 57.27 ± 1.18% (w/w) after three successive cycles of lactose hydrolysis in UHT-milk. Overall, pectin-based hydrogels are potential solid supports for preserving the lactase activity during lactose hydrolysis reactions.