• Galacto-oligosaccharides;
  • β-Galactosidase;
  • Immobilized enzyme;
  • Packed-bed reactor


The preparation of galacto-oligosaccharides (GOSs) was studied using the immobilized recombinant β-galactosidase from Aspergillus candidus CGMCC3.2919. The optimal pH and temperature for the immobilized enzyme were observed at pH 6.5 and 40°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 β-galactosidase has potential application for GOS production.