Title
Biochemical and structural characterization of the glucan and fructan exopolysaccharides synthesized by the Lactobacillus reuteri wild-type strain and by mutant strains
Author
Centraal Instituut voor Voedingsonderzoek TNO TNO Voeding
van Geel-Schutten, G.H.
Faber, E.J.
Smit, E.
Bonting, K.
Smith, M.R.
ten Brink, B.
Kamerling, J.P.
Vliegenthart, J.F.G.
Dijkhuizen, L.
Publication year
1999
Abstract
Lactobacillus reuteri LB 121 cells growing on sucrose synthesize large amounts of a glucan (D-glucose) and a fructan (D-fructose) with molecular masses of 3,500 and 150 kDa, respectively. Methylation studies and 13C or 1H nuclear magnetic resonance analysis showed that the glucan has a unique structure consisting of terminal, 4-substituted, 6-substituted, and 4,6- disubstituted alpha-glucose in a molar ratio of 1.1:2.7:1.5:1.0. The fructan was identified as a (2 → 6)-beta-D-fructofuranan or levan, the first example of levan synthesis by a Lactobacillus species. Strain LB 121 possesses glucansucrase and levansucrase enzymes that occur in a cell-associated and a cell-free state after growth on sucrose, raffinose, or maltose but remain cell associated during growth on glucose. Sodium dodecyl sulfate- polyacrylamide gel electrophoresis of sucrose culture supernatants, followed by staining of gels for polysaccharide synthesizing activity with sucrose as a substrate, revealed the presence of a single glucansucrase protein of 146 kDa. Growth of strain LB 121 in chemostat cultures resulted in rapid accumulation of spontaneous exopolysaccharide-negative mutants that had lost both glucansucrase and levansucrase (e.g., strain K-24). Mutants lacking all levansucrase activity specifically emerged following a pH shiftdown (e.g., strain 35-5). Strain 35-5 still possessed glucansucrase and synthesized wild- type glucan.
Subject
Fructan
Glucan
Polysaccharide
Bacterial growth
Carbohydrate analysis
Carbohydrate synthesis
Food industry
Lactobacillus reuteri
Methylation
Nonhuman
Lactobacillus reuteri
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http://resolver.tudelft.nl/uuid:44f17497-d556-42a8-bc0d-4471205a78d8
TNO identifier
235077
ISSN
0099-2240
Source
Applied and Environmental Microbiology, 65 (65), 3008-3014
Document type
article