Production of galacto‐oligosaccharides by immobilized recombinant β‐galactosidase from Aspergillus candidus

The preparation of galacto-oligosaccharides (GOSs) was studied using the immobilized recombinant beta-galactosidase from Aspergillus candidus CGMCC3.2919. The optimal pH and temperature for the immobilized enzyme were observed at pH 6.5 and 40 degrees C, respectively. Increasing the initial lactose concentration increased the yield of GOSs. The dilution rate was found to be a key factor during the continuous production of GOSs. The maximum productivity, 87 g/L.h was reached when 400 g/L lactose was fed at dilution rate of 0.8/h. The maximum GOS yield reached 37% at dilution rate of 0.5/h. Continuous operation was maintained for 20 days in a packed-bed reactor without apparent decrease in GOS production. The average yield of GOSs was 32%, corresponding to the average productivity of 64 g/L.h, which implied that the immobilized recombinant beta-galactosidase has potential application for GOS production.