Enzyme-Mediated Reactions of Oligosaccharides and Polysaccharides

Two types of enzymatic reactions are given here as examples of synthetic problems encountered in industry. In the first case, commercially available -D-galactosidase from Escherichia coli was used as a catalyst to transfer galactose from -lactose to oligosaccharides. A preference for galactosyl transfer to the 3- or 4-position of the sugar moiety of the oligosaccharide was observed for the products. As expected, only the -anomer was produced. A wide variety of sugars, including disaccharides, trisaccharides, cellotetraose, and maltodextrins, has been shown to act as acceptors, yielding oligosaccharides. In the second example, -galactomannan that had been previously treated to contain cationic groups (cationic guar gum) was subjected to treatment with a series of inexpensive commercial enzymes such as lipases, protease, and cellulases. Some enzyme preparations showed significant changes in the viscosities of 1% cationic guar solution. For example, lipases from Aspergillus niger and Aspergillus saitoi and protease XIII from Rhizopus niveus produced a substantial viscosity reduction (0–20% of original viscosity). These examples demonstrate the utility of low-cost enzymes in manipulating polymer structures.