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Title: ALTERNANSUCRASE MUTANTS OF LEUCONOSTOC MESENTEROIDES STRAINS NRRL B-21138

Author
item Leathers, Timothy
item Ahlgren, Jeffrey
item Cote, Gregory

Submitted to: Journal of Industrial Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Domestic replacements are needed for certain imported commodities. At the same time, new value-added markets are needed for American agriculture. For example, the United States currently imports about 25 million pounds of gum arabic, principally from the Sudan. Gum arabic is important in food processing, and has other industrial applications. However, imported material is available only at unreliable supply, quality and price. A novel natural gum from a microorganism has recently been shown to be a potential substitute for gum arabic. Furthermore, this gum can be made by fermentation of natural sugar currently produced by American farmers. However, currently available organisms do not produce gum in sufficient yields or purity to merit commercialization. We developed new and improved microorganisms, including one that produces this novel gum in enhanced yield and purity. These microorganisms will facilitate further studies of this gum, including feasibility studies for commercial applications. This work will be of interest both to basic researchers in the field and to manufacturers seeking new biomaterials.

Technical Abstract: We mutagenized Leuconostoc mesenteroides strain NRRL B-21138, a mutant strain that secretes alternansucrase with little or no contaminating dextransucrase, and screened survivors for further alterations in enzyme or polysaccharide production. Second generation mutants included highly stable strain NRRL B-21297, which produced fourfold elevated levels of alternansucrase without an increase in the proportion of dextransucrase activity. Such alternansucrase overproduction strains will facilitate studies of this enzyme and may become valuable for commercial production of alternansucrase. Another highly stable mutant strain, NRRL B-21414, grew slowly on sucrose with negligible production of polysaccharide or extracellular sucrase activity. This strain may prove useful as an expression host for glucansucrase genes.