Lactic acid bacteria-derived α-glucans: From enzymatic synthesis to miscellaneous applications

Lactic acid bacteria (LAB) are capable of producing a variety of exopolysaccharide alpha-glucans, such as dextran, mutan, reuteran, and alternan. Their structural diversity allows LAB-derived alpha-glucans to hold vast commercial value and application potential in the food, cosmetic, medical, and biotechnology fields, garnering much attention in recent years. Glycoside Hydrolase 70 family (GH70) enzymes are efficient tools for the biosynthesis of alpha-glucans with various sizes, linkage compositions, and degrees of branching, using renewable and low-cost sucrose and starch as substrates. To date, plenty of various LAB-derived GH70 glucansucrases (especially dextransucrase) have been biochemically characterized to synthesize alpha-glucans from sucrose with a variety of structural organizations. This review mainly aimed at the biotechnological synthesis of alpha-glucans using GH70 family enzymes and their diverse (potential) applications. The purification, structural analysis and physicochemical properties of alpha-glucan polysaccharides were reviewed in detail. Synchronously, some new insights and future perspectives of LAB-derived alpha-glucans enzymatic synthesis and applications were also discussed. To expand the range of applications, the physicochemical properties and bioactivities of LAB-derived alpha-glucans, other than dextran, should be further explored. Additionally, screening novel GH70 subfamily starch-acting enzymes is conducive to expanding the repertoire of alpha-glucans.