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

Abstract

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 α-(1–6) glycosidic linkages and a smaller amounts of branches derived from α-(1–2), α-(1–3), and α-(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.

Glycosyltransferases Expression Changes in Leuconostoc mesenteroides subsp. mesenteroides ATCC 8293 Grown on Different Carbon Sources

“…Although sucrose has been generally recognized as the inductor in GTFs expression in Leuconostoc strains, the mechanism behind GTFs regulation has yet to be demonstrated [22]. Very few works deal in detail with the eventual physiological mechanism; instead, most reports related to regulation limit their scope to report the differences in total GTF activity in response to environmental changes, such as carbon source [21], temperature [56,57], or oxygen availability [58,59]. D-xylose is a major component of cell walls in plants, and therefore, a carbon source for Leuconostoc bacteria since their ecological niche is vegetal matter and roots [3].…”

“…Recent work suggests that GTFs in Weissella cibaria C2-32 may be regulated by TF LexA, a protein involved in the SOS response system [57]. In Escherichia coli growing in normal conditions, dimeric LexA binds to the DNA strand and represses DNA repair genes; meanwhile, in severe culture conditions, such as low pH-, LexA forms aggregates with a lower capacity to repress transcription [64].…”

Advances in the Use of Beneficial Microorganisms to Improve Nutritional and Functional Properties of Fermented Foods

“…The modulation of fermentation parameters (native or sprouted cereal and legume flour, DY, and temperature) can lead to the production of a dextran-enriched sourdough that is suitable for the production of bread with enhanced nutritional quality (low HI and pGI), functionality (high soluble and total fiber content), and sensory attributes [ 2 ]. Some aspects related to the production of EPS by a Weissella cibaria strain were explored in depth by De Bellis et al [ 3 ]. The strain selected as a high-EPS producer in the presence of sucrose was used to produce an EPS-enriched sourdough suitable for use as a fat replacer in baked goods [ 4 ].…”

“…The strain selected as a high-EPS producer in the presence of sucrose was used to produce an EPS-enriched sourdough suitable for use as a fat replacer in baked goods [ 4 ]. The authors characterized the EPS produced by W. cibaria C43-11 and investigated the possible genetic regulatory elements responsible for the modulation of dextransucrase (dsr) gene expression [ 3 ].…”