Immobilized beta-glucosidase for the winemaking industry: study of biocatalyst operational stability in laboratory-scale continuous reactors

The stability of beta-glucosidase immobilized on chitosan pellets was studi ed under operational conditions in continuous stirred tank membrane reactor s. The rate of enzyme deactivation was monitored at 25 degrees C using p-ni trophenyl beta-D-glucopyranoside as model substrate. The medium was also su pplemented with chemicals present in the wines, namely fructose, ethanol, n erol, linanol and geraniol. Fructose did not decrease biocatalyst stability , while alcohol affected enzyme half-life from 2586 h at 3% (w/v) ethanol t o 1378 h at 12% (w/v). The addition of terpenols to solution containing 10% (w/v) alcohol reduced the half-life by a further 10%. Enzyme stability was not dependent on substrate concentration and was considered satisfactory f or an industrial process (half-life 1.2 years). These results were independ ent of the use of wet stored pellets or of samples freeze-dried (24 h at -6 0 degrees C). No added chemical influenced enzyme specific activity up to t he tested limits: fructose 20 mM, terpenols 5 ppm each, ethanol 12% (w/v). (C) 1999 Elsevier Science Ltd. All rights reserved.