Enzymatic synthesis of oligosaccharides : Kinetics, process parameters, and reactor design

The intestinal microflora, e.g. bifidobacteria, has a strong influence on the human health. Two approaches exist to increase the number or activity of health-promoting organisms in the gastrointestinal tract. Organism (probiotics) or a selective carbon source (prebiotics) can be added to the food. Examples of prebiotics are oligosaccharides. These can be produced by enzymatic synthesis with a glycosidase as catalyst and a disaccharide as substrate.Oligosaccharide formation using the transferase activity of glycosidases is a kinetically controlled reaction. Describing the concentrations of all reactants in time is essential for a reactor design. Along with describing the concentrations in time, more knowledge is obtained about the effect of process parameters such as substrate concentration, temperature, time, enzyme origin, and reactor configuration on the oligosaccharide synthesis. The model system used is the reaction with lactose as a substrate and a β-galactosidase as catalyst.A galactosyl-enzyme complex based model is used to describe the concentrations in time. The effect of temperature is implemented in the kinetic model. The model is used to describe the synthesis by β-galactosidases from various mesophilic and thermophilic enzymes. Three possibilities (adsorption, membranes, and ion-exchange chromatography) are discussed to remove trisaccharides from the reaction mixture and thereby increase the yield. Finally, the possibility to produce oligosaccharides in water-miscible solvents is discussed