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United States Department of Agriculture

Agricultural Research Service

Title: Some Structural Features of An Insoluble Alpha-D-Glucan from a Mutant Strain of Leuconostoc Mesenteroides Nrrl B-1355

Authors
item Cote, Gregory
item Ahlgren, Jeffrey
item Smith, Michael

Submitted to: Journal of Industrial Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 2, 1999
Publication Date: N/A

Interpretive Summary: New products are needed from farm commodities to improve the economy and create American agribusiness jobs. Certain microbes convert sugars, derived from crops, into gums which can be useful in foods and for industrial applications. In this study, a mutant bacterial strain was found not to produce the highly soluble (able to dissolve in water) gums of the parent strain. Instead, it produced a gum which did not dissolve in water. This gum was found to be very different in chemical structure from the gums produced by the parent strain. This suggests that very minor mutations can lead to significant changes in the chemical structures and physical properties of these gums. This information will lead to a better understanding of how these gums are produced. This should eventually allow us to custom tailor similar materials for food and industrial applications at will. The work is of interest to scientists in the field of carbohydrate biochemistry and to commercial gum producers.

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 which produces practically no soluble polysaccharide, but significant amounts of an insoluble D-glucan. Methylation analysis shows it to contain linear (1-3) and (1-6) linkages, as well as (1-2) and (1-3) branch linkages. 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 soluble dextranase-limit fraction with an (1-2) debranching enzyme led to further dextranase susceptibility. Methylation, FTIR, and NMR analyses of the various dextranase-treated fractions indicate a non-uniform structure with domains bearing similarities to Leuconostoc mesenteroides strain NRRL B-1299 dextran and to insoluble streptococcal D-glucans.

Last Modified: 10/20/2014
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