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United States Department of Agriculture

Agricultural Research Service

Title: A Mutant Strain of Leuconostoc Mesenteroides B-1355 Producing a Glucosyltransferase Synthesizing A(1-2) Glucosidic Linkages

Authors
item Smith, Michael
item Zahnley, James
item Wong, Rosalind
item Lundin, Robert
item Ahlgren, Jeffrey

Submitted to: Journal of Industrial Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 23, 1998
Publication Date: N/A

Interpretive Summary: Microrganisms like Leuconostoc mesenteroides produce enzymes that may be applied to build useful polymers like dextrans from cheap starting materials like sugar. Some of the enzymes produce very specialized bonds and, if purified, could facilitate engineering of polymer properties to specific end uses. Starting from strain B-1355, we developed three mutants each of which produces an enzyme that catalyzes formation of a unique polymer with a specific linkage between glucose subunits. The research not only identified colony property differences between the strains but also the uniqueness of the three linkage-forming enzymes. The research demonstrates how to generate and identify additional bacteria strains to synthesize novel dextrans with potentially useful commercial properties.

Technical Abstract: Mutant strains of Leuconostoc mesenteroides strain B-1355 were isolated which produced predominantly single glucosyltranserease (GTF) activity bands on SDS gels. Cultures of strain R1510 produced GTF-1 (244 kDa), while cultures of strains R1588 and R1554 alternansucrase (204 kDa). Strains SL-1 and LC-4 produced high levels of dextransucrase (172 kDa). The mutants produced three types of polysaccharides based on colony morphology on 10% (wt/vol) sucrose agar, trisaccharides produced from alpha-methyl-D-glucoside and sucrose, and GTF activities on SDS gels. Strain R1510 synthesized trisaccharides which were resistant to hydrolysis with amyloglucosidase, and whose HPLC peaks eluted with the same retention times, relative to alpha-methyl-isomaltose and alpha-methyl-isomaltotriose, as those from strain B-1299 (which contain alpha(1-2) linkages). Prolonged boiling was required to degrade GTF-1 or dextransucrase to fragments, making it unlikely that GTF-1 contained subunits of other GTFs. GTFs synthesizing alpha (1-2) linkages have not been described previously in strain B-1355 and their unrecognized presence could complicate estimates of alternansucrase production.

Last Modified: 7/23/2014
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