Production of isomelezitose from sucrose by engineered glucansucrases

Abstract

Certain lactic acid bacteria produce glycosyltransferases known as glucansucrases, which synthesize α-D-glucans via glucosyl transfer from sucrose. We recently reported on the formation of the unusual trisaccharide isomelezitose in low yields by a variety of glucansucrases. Isomelezitose is a rare non-reducing trisaccharide, with the structure α-d-glucopyranosyl- (1→6)-β-d-fructofuranosyl-(2↔1)-α-d-glucopyranoside. In this work, we describe the synthesis of isomelezitose in high yields by variants of glucansucrases engineered to contain a single point mutation at a key leucine residue involved in acceptor substrate binding. Some variants produce isomelezitose in yields up to 57%. This method is amenable to large-scale production of isomelezitose for food, industrial and biomedical applications.