Characterization of the heteropolysaccharides produced by Liquorilactobacillus sicerae CUPV261 and Secundilactobacillus collinoides CUPV237 isolated from cider.

Some lactic acid bacteria (LAB) strains isolated from alcoholic beverages are able to produce exopolysaccharides (EPS). The present work focuses on the physico-chemical characterization of the heteropolysaccharides (HePS) produced by Liquorilactobacillus sicerae CUPV261T (formerly known as Lactobacillus sicerae) and Secundilactobacillus collinoides CUPV237 (formerly known as Lactobacillus collinoides) strains isolated from cider. Genome sequencing and assembly enabled the identification of at least four putative HePS gene clusters in each strain, which correlated with the ability of both strains to secrete EPS. The crude EPS preparation from CUPV261T contained glucose, galactose and rhamnose, and that of CUPV237 was composed of glucose, galactose and N-acetylglucosamine. Both EPS were mixtures of HePS of different composition, with two major soluble components of average molecular weights (Mw) in the range of 106 and 104 g.mol-1. These HePS were resistant to gastric stress conditions in an in vitro model, and they significantly reduced zebrafish larvae mortality in an in vivo model of inflammatory bowel disease.

Production and partial characterization of exopolysaccharides produced by two Lactobacillus suebicus strains isolated from cider.

Many lactic acid bacteria synthesize extracellular polysaccharides (exopolysaccharides, EPSs) with a large variation in structure and potential functional properties. Although EPS production can produce detrimental effects in alcoholic beverages, these polymers play an important role in the rheological behavior and texture of fermented products. In this work, EPS production by two Lactobacillus suebicus strains, which were isolated from ropy ciders, was examined in a semidefined medium. The existence of priming glycosyltransferase encoding genes was detected by PCR. In addition, the preliminary characterization of the polymers was undertaken. Molecular masses were determined by size exclusion chromatography revealing the presence of two peaks, corresponding to polymers of high- and low-molecular-weight in all fractions. The composition of the EPS fractions was analyzed by gas chromatography-mass spectrometry after acid hydrolysis, revealing that they contained glucose, galactose, N-acetylglucosamine and phosphate, although in different ratios, suggesting that a mixture of polysaccharides is being synthesized. We also examined the influence of the sugar source (glucose, ribose, xylose, or arabinose) and pH conditions on growth and EPS production.