Mathematical Modelling of Galactooligosaccharides Synthesis: Insights into Aspergillus oryzae Derived β-Galactosidase Kinetics

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The objective of this study was to adapt experimental data with a mathematical model based on transgalactosylation mechanisms identified in the literature for the synthesis of galactooligosaccharides and lactose hydrolysis. Galactooligosaccharides, synthesized from lactose through β-galactosidase-catalyzed transgalactosylation reactions, are acknowledged as specific bifidogenic factors among prebiotic carbohydrates. Modelling galactooligosaccharide synthesis is challenging due to simultaneous hydrolysis and transferase reactions with identical nucleophiles and substrates. Therefore, researchers tried to simplify the mechanism by ignoring intermediate reactions or inhibitory effects of glucose and galactose. This study explored various kinetic models, considering the complexity of the reaction mechanism and balancing accuracy with feasibility. Experimental data from galactooligosaccharide synthesis using a continuous stirred tank reactor was adapted to kinetic models (Models A and B) with modifications, incorporating glucose and galactose inhibitions. The COPASI software was used for testing fitness of reaction models. Eight models were evaluated for their suitability, utilizing six replicated experimental datasets under specific reaction conditions, including a temperature of 45°C, lactose concentration of 18.25°Brix, and enzyme concentration of 10-unit g lactose solution-1. The analysis was conducted using the "random research" and "particle swarm" algorithms. Model evaluations revealed that Model B, augmented with glucose and galactose inhibitions, provided the closest alignment between experimental and simulated data. The study underscored the significance of glucose and galactose impacts on galactooligosaccharide synthesis efficiency. The Model B, with addition of glucose and galactose inhibitions, emerged as a valuable tool for predicting galactooligosaccharide yield, contributing to a deeper understanding of A.oryzae-derived β-galactosidase kinetics due to its significant influence on parameters such as productivity, conversion of lactose, and composition of product. The findings will guide optimization strategies for enhanced galactooligosaccharide production efficiency, advancing knowledge in enzymatic galactooligosaccharide synthesis.