Kinetics and design relation for enzymatic conversion of lactose into galacto-oligosaccharides using commercial grade β-galactosidase.

The enzymatic synthesis of galacto-oligosaccharides (GOS) from lactose was studied using commercial grade β-galactosidase (Biolacta FN5) from Bacillus circulans. The reaction was carried out under free enzyme condition varying initial lactose concentration (ILC: 55-525 g/L), enzyme concentration (0.05-1.575 g/L), temperature (30-50°C) and pH (5.0-6.0). Reaction mixture compositions were analyzed utilizing high performance liquid chromatography (HPLC). A maximum GOS formation of 39% (dry basis) was achieved at an ILC of 525 g/L converting 60% of the lactose fed. Tri-saccharides were the major types of GOS formed, accounting approximately 24%; whereas, tetra-saccharides and penta-saccharides account approximately 12% and 3%, respectively. Design correlation was developed in order to observe the quantitative effect of operating parameters on GOS yield. Further, based on Michaelis-Menten model, four-step reaction pathways were considered for simplistic understanding of the kinetics. Apart from predicting the reaction mixture composition, the approach also provided kinetic parameters though simulation using COPASI 4.7®. Excellent agreements were observed between simulated and experimental results.