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Glucansucrase was purified from Leuconostoc pseudomesenteroides. The glucansucrase exhibited maximum activity at pH 5.5 and 30 °C. Ca2+ significantly promoted enzyme activity. An exopolysaccharide (EPS) was synthesized by this glucansucrase in vitro and purified. The molecular weight of the EPS was 3.083 × 106 Da. Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy showed that the main structure of glucan was 97.3% α-(1→6)-linked D-glucopyranose units, and α-(1→3) branched chain accounted for 2.7%. Scanning electron microscopy (SEM) observation of dextran showed that its surface was smooth and flaky. Atomic force microscopy (AFM) of dextran revealed a chain-like microstructure with many irregular protuberances in aqueous solution. The results showed that dextran had good thermal stability, water holding capacity, water solubility and emulsifying ability (EA), as well as good antioxidant activity; thus it has broad prospects for development in the fields of food, biomedicine, and medicine.

Glucansucrase (GS) belongs to the GH70 family, which not only can synthesize exopolysaccharides (EPSs) with different physicochemical properties through glucosyl transglycosylation (by hydrolyzing sucrose) but can also produce oligosaccharides. Different strains produce different GSs, which catalyze the synthesis of EPS with different glycosidic bond structures; these EPSs have different biological functions. As an important enzymatic tool, GS has great potential in health care medicine, biological materials, ecological protection, the food chemical industry, etc. GS is mainly produced by lactic acid bacteria (LAB), including Leuconostoc, Streptococcus, Lactobacillus, and Weissella species. With the elucidation of the crystal structure of GS and the advancement of genome sequencing technology, its synthesis reaction mechanism and specific structural characteristics are gradually becoming clear. This review summarizes the isolation, purification, physical and chemical properties, detection methods, sources, and applications of GS in order to provide a reference for the research and development of GS.