Immobilization of cell wall invertase in a polyacrylamide hydrogel for invert sugar production

Abstract

Cell wall invertase (CWI) from Saccharomyces cerevisiae was immobilized in polyacrylamide hydrogels. The aim of the development of a new biocatalyst was to obtain an improved enzyme for invert sugar production. The monomer concentration and enzyme amount in the immobilizate were optimized, and the obtained biocatalyst had an enzyme activity of 138 +/- 6 IU g(-1). The pH and temperature optima were 4.0 and 70 degrees C, respectively. The stability of immobilized enzyme was determined at several temperatures in the absence of substrate and the half-life obtained at 50 degrees C was 81 days, at 60 degrees C, 128 min and at 70 degrees C, 1.24 min. The biocatalyst was tested at low pH values, 3.0 and 3.5 were tested, and showed great stability. The KM values were 34.1 +/- 1.7 and 126.2 +/- 6.3 mM for free and immobilized CWI, respectively. The activation energies were 37.7 and 23.0 kJ mol(-1) for free and immobilized CWI, respectively. Cell wall invertase immobilized in polyacrylamide hydrogel (CWI-PAA) was tested for the production of high concentrated invert sugar in a batch and a packed bed reactor. After five days of continuous process, the quality and characteristics of the produced invert sugar remained unchanged.