Immobilization of enological pectinase in calcium alginate hydrogels: A potential biocatalyst for winemaking

Abstract

A biocatalyst was obtained by immobilizing an enological commercial pectinase within calcium alginate hydrogels using an entrapment technique, and its catalytic activity was evaluated during different storage conditions. Hydrogel beads were stored at 4 °C in three different ways: (i) wet, in citrate buffer solution (pH 3.8); (ii) dehydrated by using a vacuum stove; and (iii) freeze-dried. Biocatalyst surface and their internal morphology were characterized by Scanning Electron Microscopy and a good enzyme distribution throughout alginate matrix was observed. Fourier Transform Infrared Spectroscopy results confirmed the presence of absorption bands associated with amino groups present in enzymes. Immobilization procedure did not modify the optimal pH and temperature (pH = 4.0 and 20 °C) for pectinase activity, comparing to free enzyme. Entrapped pectinase showed activity until six reaction cycles with 40% residual activity. Storage stability studies demonstrated that wet entrapped pectinase retained its initial enzymatic activity up to 11 weeks, whereas that lyophilized hydrogels retained its original activity after 8 months of storage. These results suggest that immobilized pectinase may be successfully exploited in various industrial applications, with special concern in grape juice clarification process. Thus, the turbidity of grape must decreased significantly using the immobilized pectinase during 150 min at 20 °C. This biocatalyst could be easily removed after clarification process and it can be reused, minimizing production economic costs in wine industry.