Assessment of repetitive batch-wise synthesis of galacto-oligosaccharides from lactose slurry using immobilised β-galactosidase from Bacillus circulans

The synthesis of galacto-oligosaccharides (GOS) using covalently immobilised β-galactosidase from Bacillus circulans was carried out in a lactose slurry rather than in solution. Repeated batch-wise synthesis at 58 °C and 55% (w/w) lactose could be carried out for at least 15 successive runs. All 15 runs were completed within 4 h of reaction time. The reduction of heat exposure due to these short incubation times contributed to the retention of 60% of the initial activity. The product properties of the GOS mixture obtained with the immobilised biocatalyst were compared with the free enzyme product. Oligosaccharide yields and product pattern were highly similar as was the degree of polymerisation. The productivity of the immobilised enzyme system was compared to the free enzyme. The enzymatic productivity (i.e., g GOS g−1 enzyme) after 15 consecutive runs was 165% higher for the immobilised enzyme than for the free enzyme.