CHARACTERIZATION OF THE DIFFERENT DEXTRANSUCRASE ACTIVITIES EXCRETED IN GLUCOSE, FRUCTOSE, OR SUCROSE MEDIUM BY LEUCONOSTOC-MESENTEROIDES NRRL B-1299

When grown in glucose or fructose medium in the absence of sucrose, Le uconostoc mesenteroides NRRL B-1299 produces two distinct extracellula r dextransucrases named glucose glucosyltransferase (GGT) and fructose glucosyltransferase (FGT). The production level of GGT and FGT is 10 to 20 times lower than that of the extracellular dextransucrase sucros e glucosyltransferase (SGT) produced on sucrose medium (traditional cu lture conditions), GGT and FGT were concentrated by ultrafiltration be fore sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysi s. Their molecular masses were 183 and 186 kDa, respectively, differin g from the 195 kDa of SGT. The structural analysis of the dextran prod uced from sucrose and of the oligosaccharides synthesized by acceptor reaction in the presence of maltose showed that GGT and FGT are two di fferent enzymes not previously described for this strain. The polymer synthesized by GGT contains 30% alpha(1-->2) linkages, while FGT catal yzes the synthesis of a linear dextran only composed of alpha(1-->6) l inkages.