Characterization of Dextran Produced by the Food-Related Strain Weissella cibaria C43-11 and of the Relevant Dextransucrase Gene

A metabolic feature of lactic acid bacteria (LAB) is the production of exopolysaccharides (EPSs), which have technological and functional properties of interest to the food sector. The present study focused on the characterization of the Weissella cibaria strain C43-11, a high EPS producer in the presence of sucrose, in comparison with a low-producing strain (C2-32), and on possible genetic regulatory elements responsible for the modulation of dextransucrase (dsr) genes expression. NMR analysis of the polymeric material produced by the C43-11 strain indicated the presence of dextran consisting mainly of a linear scaffold formed by alpha-(1-6) glycosidic linkages and a smaller amounts of branches derived from alpha-(1-2), alpha-(1-3), and alpha-(1-4) linkages. Molecular analysis of the dsr genes and the putative transcriptional promoters of the two strains showed differences in their regulatory regions. Such variations may have a role in the modulation of dsr expression levels in the presence of sucrose. The strong upregulation of the dsr gene in the C43-11 strain resulted in a high accumulation of EPS. This is the first report showing differences in the regulatory elements of the dsr gene in W. cibaria and indicates a new perspective of investigation to identify the regulatory mechanism of EPS production.

Automated summary

Lactic acid bacteria can produce exopolysaccharides (EPS) with technological and functional properties for the food sector. This study focused on the characterization of high EPS-producing strain W. cibaria C43-11 in the presence of sucrose, compared to a low-producing strain C2-32, and investigated the genetic regulatory elements responsible for the modulation of dextransucrase (dsr) gene expression. NMR analysis revealed the composition of the EPS produced by C43-11 strain, which consists of a linear scaffold with glycosidic linkages and branches. Molecular analysis showed differences in the regulatory regions of dsr genes between the two strains. The upregulation of dsr gene in C43-11 strain resulted in a high accumulation of EPS. This study provides a new perspective for investigating the regulatory mechanism of EPS production.