Kinetic Model for Galacto-Oligosaccharide Synthesis

A new micro-kinetic model is proposed for galacto-oligosaccharide (GOS) synthesis with β-galactosidase from Aspergillus oryzae. Several kinetic models with similar reaction mechanisms, i.e., steps and kinetic constants, have been investigated covering a range of initial lactose (20-40 wt %) and enzyme concentrations (0.5-2 mg/mL). The kinetic parameters were estimated simultaneously for all experimental results using a hybrid genetic algorithm. A detailed analysis of the effect of process parameters on the concentrations of lactose and GOS is performed. The proposed model has a very good quantitative fit of the experimental data, with an average error of 9.34%. More importantly, qualitative trends for the change in the concentration of lactose and GOS are predicted excellently, especially if one takes into account the variation of both concentrations of enzyme and lactose in a range wider than reported in the literature to date. Also, the analysis between the two comparative reactions of transglycosylation and lactose hydrolysis confirmed the positive effect of increasing lactose concentration on the production of GOS. On the other hand, a higher enzyme concentration resulted in a faster production of GOS but with more intensive decomposition at longer reaction times.