Submitted to: Carbohydrate International Symposium
Publication Type: Abstract Only
Publication Acceptance Date: August 14, 1998
Publication Date: N/A
Technical Abstract: Leuconostoc mesenteroides strain NRRL B-1355 produces two soluble extracellular alpha-D-glucans from sucrose, namely, alternan and dextran. An unusual mutant strain derived from B-1355 has recently been isolated by WRRC scientists which produces practically no soluble polysaccharide but significant amounts of an insoluble polysaccharide. FTIR indicates that this insoluble D-glucan lacks contiguous alpha- (1-3) linkages. Methylation analysis shows it to contain linear (1-3) and (1-6) linkages as well as (1-2) and (1-3) branch linkages. Clear NMR spectra could not be obtained. The insoluble glucan was partially digestible by endodextranase, giving rise to a series of oligosaccharides, a high-molecular weight soluble fraction, and an insoluble residue. Treatment of the dextranase-limit fractions with an alpha-(1-2) debranching enzyme led to further dextranase susceptibility. These results, in conjunction with methylation and NMR analysis of the various dextranase-treated fractions, indicate a strong similarity to Leuconostoc mesenteroides strain NRRL B-1299 dextran. It is not entirely clear whether this represents an altered glucansucrase specificity arising from mutational changes in the native glucansucrases or an increase in an enzyme activity present in B-1355 at trace levels, coupled with an absence of destransucrase and alternansucrase activities.