Exopolysaccharides from co-cultures of Weissella confusa 11GU-1 and Propionibacterium freudenreichii JS15 act synergistically on wheat dough and bread texture.

The storage of bread is limited by both physical (staling) and microbial (mainly fungal) spoilage. Exopolysaccharides (EPS) produced by lactic acid bacteria (LAB) and organic acids from propionibacteria (PAB) have been used to enhance texture and extend shelf-life of bakery products. In this study the functionality of EPS of Weissella confusa A3/2-1 (dextran), W. confusa F3/2-2 (dextran and levan), W. confusa 11GU-1 (dextran and ropy capsular polysaccharide) was evaluated in wheat bread. Two strains of Propionibacterium freudenreichii (Pf), shown to produce a heteropolysaccharide (Pf JS15) or a ß-glucan (Pf DF30), were tested in single and mixed cultures with W. confusa (Wc). The EPS fermentates were prepared by batch fermentation of cereal- or malt-based medium using sucrose (Wc) or lactic acid (Pf) as carbon source. Incorporation of EPS from single culture fermentates and 1:1 Weissella-Propionibacterium fermentate mixtures revealed strong positive effects of dextran and ropy capsular polysaccharide produced by Wc 11GU-1 on bread staling retardation, with synergistic effects of EPS mixture from Wc 11GU-1 and Pf JS15. A co-fermentation of Wc 11GU-1 and Pf JS15 was developed to produce EPS together with antifungal organic acid mixture (acetate and propionate) in a single step process. The addition of 15% (w/w flour base) co-culture, yielding EPS, acetate and propionate concentrations of 1.5, 0.5 and 1g/kg dough, respectively, resulted in improved bread texture, increased loaf volume and decreased crumb firming during storage for 3days compared with control breads and breads supplemented with equivalent levels of chemical organic acids. Our data showed that EPS could compensate for the negative effects of chemical acetate and propionate in a concentration range exerting antifungal effects. The natural bioingredient produced by Wc 11GU-1 and Pf JS15 has potential for applications as antifungal, texture-building and anti-staling agent in breads, consistent with consumer demands for clean label products.

Characterization of exopolysaccharide and ropy capsular polysaccharide formation by Weissella.

With their broad functional properties, lactic acid bacteria derived high molar mass exopolysaccharides (EPS) and oligosaccharides are of great interest for food, medical and pharmaceutical industry. EPS formation by 123 strains of Weissella cibaria and Weissella confusa, was evaluated. Dextran formation from sucrose was observed for all tested strains while 18 strains produced fructan in addition to dextran. Six isolates synthesized a highly ropy polymer from glucose associated with the formation of a cell-bound, capsular polysaccharide (CPS) composed of glucose, O-acetyl groups and two unidentified monomer components. The soluble EPSs of nine strains were identified as low α-1,3-branched dextran, levan and inulin type polymers using NMR. In addition to glucan and fructan, W. confusa produced gluco- and fructooligosaccharides. Partial dextransucrase and fructansucrase sequences were characterized in the selected Weissella strains. Our study reports the first structural characterization of fructan type EPS from Weissella as well as the first Weissella strain producing inulin. Production of more than one EPS-type by single strains may have high potential for development of applications combining EPS technological and nutritional benefits.