Glucansucrase is an enzyme classified as a glycoside hydrolase (GH) 70 family, which catalyzes the synthesis of glucooligosaccharides with a low molecular weight using sucrose as a donor of D-glucopyranose and maltose as a carbohydrate acceptor. In this study, glucansucrase-producing lactic acid bacteria strain was isolated from the fermented foods collected in traditional markets, and the optimum conditions for the oligosaccharide production were investigated. The strain CCK940 isolated from Chinese cabbage kimchi was selected as an oligosaccharide-producing strain due to its high glucansucrase activity, with 918.2 mU/mL, and identified as Leuconostoc lactis. The optimum conditions for the production of oligosaccharides using Leu. lactis CCK940 were to adjust the initial pH to 6.0, add 5% (w/v) sucrose and 10% (w/v) maltose as a donor and acceptor molecules, respectively, and feed 5% (w/v) sucrose at 4 and 8 h of cultivation. When Leu. lactis CCK940 was cultured for 12 h at optimum conditions, at least four oligosaccharides with a polymerization degree of 2-4 were produced.

Glucansucrases are members of GH70 family of glycoside hydrolases and mainly produced by lactic acid bacteria such as Leuconostoc, Lactobacillus, and Weisella species. Glucansucrases use sucrose as a substrate to synthesize glucans as well as to produce oligosaccharides by transferring glucose moiety from sucrose onto acceptor carbohydrate molecules. It is known that some oligosaccharides produced by the reaction of glucansucrase show functional properties such as prebiotics and immunostimulatory activities. In this study, lactic acid bacteria which produce glucansucrase were screened from a variety of fermented foods, vegetables, and fruits collected from various area of Korea. Among 149 lactic acid bacteria strains which were isolated using BCP agar plates, 8 strains were selected which showed high glucansucrase activities. By nucleotide sequence analysis of 16S rRNA gene, strain no. 26-4 and 109-4 were identified as Leuconostoc mesenteroides, strain no. 95-4 strain was L. lactis, strain no. 92-4 and 112-1 were Weissella kimchii, strain no. 94-1 and 95-1 strains were W. confusa, and strain no. 113 was W. cibaria. When the oligosaccharides produced by the reaction of glucansucrase were analyzed using Bio-LC after these lactic acid bacteria were cultured into sucrose-containing media, the chromatograms of all bacterial showed unidentified peaks which implied the newly synthesized oligosaccharides