Ana Isabel Puertas

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.

Lactobacillus sicerae sp. nov., a lactic acid bacterium isolated from Spanish natural cider.

Strains CUPV261(T) and CUPV262 were isolated from ropy natural ciders of the Basque Country, Spain, in 2007. Cells are Gram-stain positive, non-spore-forming, motile rods, facultative anaerobes and catalase-negative. The strains are obligately homofermentative (final product dl-lactate) and produce exopolysaccharides from sucrose. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the highest similarity to both isolates corresponded to the type strain of Lactobacillus vini (99.1 %), followed by Lactobacillus satsumensis (96.4 %), and Lactobacillus oeni (96.2 %), and for all other established species, 16S rRNA gene sequence similarities were below 96 %. The species delineation of strains CUPV261(T) and CUPV262 was evaluated through RAPD fingerprinting. In addition, a random partial genome pyrosequencing approach was performed on strain CUPV261(T) in order to compare it with the genome sequence of Lactobacillus vini DSM 20605(T) and calculate indexes of average nucleotide identity (ANI) between them. Results permit the conclusion that strains CUPV261(T) and CUPV262 represent a novel species of the genus Lactobacillus, for which the name Lactobacillus sicerae sp. nov. is proposed. The type strain is CUPV261(T) ( = CECT 8227(T) = KCTC 21012(T)).

Draft Genome Sequence of Pediococcus parvulus 2.6, a Probiotic β-Glucan Producer Strain

ABSTRACT We report here the draft genome sequence of the probiotic Pediococcus parvulus 2.6, a lactic acid bacterial strain isolated from ropy cider. The bacterium produces a prebiotic and immunomodulatory exopolysaccharide, and this is the first strain of the P. parvulus species whose genome has been characterized.

Lactobacillus plantarum CIDCA 8327: An α-glucan producing-strain isolated from kefir grains

Lactobacillus plantarum CIDCA 8327 is an exopolysaccharide (EPS)-producer strain isolated from kefir with promising properties for the development of functional foods. The aim of the present study was to characterize the structure of the EPS synthesized by this strain grown in skim milk or semidefined medium (SDM). Additionally, genes involved in EPS synthesis were detected by PCR. L. plantarum produces an EPS with a molecular weight of 104Da in both media. When grown in SDM produce an heteropolysaccharide composed mainly of glucose, glucosamine and rhamnose meanwhile the EPS produced in milk was composed exclusively of glucose indicating the influence of the sugar source. FTIR spectra of this EPS showed signals attributable to an α-glucan. Both by 1H NMR and methylation analysis it was possible to determine that this polysaccharide is a branched α-(1→4)-d-glucan composed of 80% linear α-(1→4)-d-glucopyranosyl units and 19% (1→4)-d-glucopyranosyl units substituted at O-3 by single α-d-glucopyranosil residues.

Draft Genome Sequence of Lactobacillus collinoides CUPV237, an Exopolysaccharide and Riboflavin Producer Isolated from Cider

ABSTRACT Lactobacillus collinoides CUPV237 is a strain isolated from a Basque cider. Lactobacillus collinoides is one of the most frequent species found in cider from Spain, France, or England. A notable feature of the L. collinoides CUPV237 strain is its ability to produce exopolysaccharides.

Polyphenolic profile in cider and antioxidant power

BACKGROUND The aim of this work was to find the effect of polyphenolic compounds in Basque ciders on the following parameters: antioxidant activity, browning, protein-precipitating capacity, turbidity and reduction potential. These five parameters are highly important, as they affect the taste, the visual aspect and the preservation of cider, and are mainly related to polyphenolic compounds. RESULTS Procyanidin B1 and procyanidin B2 showed a significant positive effect on antioxidant activity. p-Coumaric acid, (-)-epicatechin and hyperin had a significant positive effect on protein-precipitating capacity. Tyrosol had a significant negative effect on reduction potential. CONCLUSION Procyanidin B1 and procyanidin B2 are the most powerful antioxidants in Basque cider, while p-coumaric acid, (-)-epicatechin and hyperin are those with greatest capacity to precipitate proteins. Ciders with higher tyrosol concentration will have less reduction potential and higher antioxidant reservoir.

Characterization of Pediococcus ethanolidurans CUPV141: A β-D-glucan- and Heteropolysaccharide-Producing Bacterium

Pediococcus ethanolidurans CUPV141 is an exopolysaccharide (EPS)-producing lactic acid bacterium, first isolated from Basque Country cider (Spain). Physicochemical analysis of the EPS synthesized by the bacterium revealed that CUPV141 produces mostly a homopolysaccharide (HoPS), characterized as a 2-substituted (1,3)-β-D-glucan, together with a small quantity of a heteropolysaccharide (HePS) composed of glucose, galactose, glucosamine, and glycerol-3-phosphate, this being the first Pediococcus strain described to produce this kind of polymer. On the contrary, an isogenic strain CUPV141NR, generated by chemical mutagenesis of CUPV141, produced the HePS as the main extracellular polysaccharide and a barely detectable amount of 2-substituted (1,3)-β-D-glucan. This HoPS is synthesized by the transmembrane GTF glycosyltransferase (GTF), encoded by the gtf gene, which has been previously reported to be located in the pPP2 plasmid of the Pediococcus parvulus 2.6 strain. Southern blot hybridization revealed that in CUPV141 the gtf gene is located in a plasmid designated as pPE3, whose molecular mass (34.4 kbp) is different from that of pPP2 (24.5 kbp). Analysis of the influence of the EPS on the ability of the producing bacteria to adhere to the eukaryotic Caco-2 cells revealed higher affinity for the human enterocytes of CUPV141NR compared to that of CUPV141. This result indicates that, in contrast to the 2.6 strain, the presence of the HoPS does not potentiate the binding ability of P. ethanolidurans. Moreover, it supports that the phosphate-containing bacterial HePS improved the interaction between P. ethanolidurans and the eukaryotic cells.