Enzyme engineering for oligosaccharide biosynthesis

Abstract

Oligosaccharides are compounds of great interest in the food and pharmaceutical industry, mainly due to their prebiotic action and other health- promoting effects, in addition to other properties, acting as lowcaloric sweeteners, antioxidants, or antimicrobial agents. Oligosaccharide functionality depends on their chemical structure, which relies on the nature of the building sugar residues, the linkage type, and the degree of polymerization. Their production is based either in the partial hydrolysis of polysaccharides or in the synthesis from other sugars with lower degree of polymerization. This methodology is described along the first part of this chapter, making special emphasis on the enzymatic-based technology, which shows clear advantages over chemical methods. Glycoside hydrolases and glycosyltransferases are the two enzyme classes involved in oligosaccharide production. They operate as highly specialized molecular tools for the generation of the different types of oligosaccharides. In the second part of the chapter, the strategies employed for improving the properties of these enzymes are explained. Enzyme engineering, through site- directed mutagenesis or directed evolution, has succeeded in delivering enzymatic variants with enhanced oligosaccharide yields, a different product profile or a wider substrate specificity. Moreover, immobilization of enzymes on solid supports through different methods has allowed their reutilization during repeated batches or their implementation in continuous systems, and, in some instances, it was also accompanied by an increased activity or stability. Overall, this chapter provides an overview about the facts and potentials of oligosaccharide production methodologies.