GLUCOOLIGOSACCHARIDES SYNTHESIZED BY GLYCOSYLTRANSFERASES FROM MUTANT STRAIN LEUCONOSTOC MESENTEROIDES M2860 AND THEIR PREBIOTIC POTENTIAL

Functional foods, of which probiotic- and prebiotic-containing foods are a subset, have recently justified the efforts of health authorities in many countries. Many strains of Leuconostoc mesenteroides synthesize extracellular transglucosydases (GTFs) capable of producing dextrans and related glucans from sucrose. In the presence of sucrose and an acceptor like maltose, they synthesize glucooligosaccharides. It was shown that the extracellular GTFs from the mutant strain Leuc. mesenteroides M2860 catalyze acceptor reactions and transfer the glucose unit from sucrose onto maltose to produce glucooligosaccharides. By increasing the sucrose/maltose ratio (S/M), it was possible to catalyze the synthesis of oligosaccharides of increasing degree of polymerisation. For an S/M ratio of 7, both linear oligosaccharides (only composed of alpha-(1- 6) linkages and a maltose residue at the reducing end) and branched oligosaccharides were produced. Some of the glucooligosaccharides synthesized contain alpha-(1- 6) osidic linkages and were completely hydrolyzed by dextranase. The other glucooligosaccharides synthesized, resisted the action of this enzyme. It could be concluded that the catalytic properties of the extracellular GTFs, as well as their pH optima and products formed are of great importance for the synthesis of different types of oligosaccharides. Branched oligosaccharides produced by GTFs coming from Leuc. mesenteroides M2860 were readily catabolized by lactobacilli but not by Escherichia coli and Listeria innocua strains, pointing toward their application in intestinal microflora modification.