Insoluble Glucan Formation by Leuconostoc mesenteroides B-1355

Leuconostoc mesenteroides B-1355 produced at least three glucosyltransferases (GTFs). We previously identified GTF-2 as alternansucrase and GTF-3 as fraction L dextransucrase. We here show that GTF-1 is a previously unreported sucrase that synthesized water-insoluble dextran. Our evidence consisted of the following. (i) GTF-1 was a major component and GTF-2 was a minor component of culture supernatant fractions, but supernatant fractions actively synthesized water-insoluble glucan. (ii) GTF-1 and culture supernatants produced an unusual high-pressure liquid chromatography pattern of malto-oligosaccharides that was not reproduced by GTF-2-GTF-3 mixtures. (iii) GTF-2, GTF-3, and GTF-2-GTF-3 mixtures did not synthesize insoluble glucan from sucrose. Nearly all of the alternansucrase in young (less than 17-h) cultures was associated with the cells.