Immobilization on chitosan of a thermophilic beta-glycosidase expressed in Saccharomyces cerevisiae.

A Sulfolobus solfataricus beta-glycosidase expressed in Saccharomyces cerevisiae (S beta gly) was immobilized on chitosan activated with glutaraldehyde. The yield of immobilization was evaluated as 80%. Compared to the free beta-glycosidase, the immobilized enzyme showed a similar pH optimum (pH = 7.0), the same increasing activity up to 80 degrees C, improved thermostability, and no inhibition by glucose. Functional studies pointed out that the kinetic constant values for both enzymes were comparable. A bioreactor, assembled with the immobilized S beta gly, was used for glucose production. The values of cellobiose conversion increased on increasing residence time in the bioreactor, following a nonlinear trend. However, the highest glucose production/min was obtained at a flow of 0.5 mL/min.