Growth and exopolysaccharide (EPS) production by Oenococcus oeni I4 and structural characterization of their EPSs

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 CUPV261^T 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 (M_w) 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.

Biological Functions of Exopolysaccharides from Lactic Acid Bacteria and Their Potential Benefits for Humans and Farmed Animals

Lactic acid bacteria (LAB) synthesize exopolysaccharides (EPS), which are structurally diverse biopolymers with a broad range of technological properties and bioactivities. There is scientific evidence that these polymers have health-promoting properties. Most commercialized probiotic microorganisms for consumption by humans and farmed animals are LAB and some of them are EPS-producers indicating that some of their beneficial properties could be due to these polymers. Probiotic LAB are currently used to improve human health and for the prevention and treatment of specific pathologic conditions. They are also used in food-producing animal husbandry, mainly due to their abilities to promote growth and inhibit pathogens via different mechanisms, among which the production of EPS could be involved. Thus, the aim of this review is to discuss the current knowledge of the characteristics, usage and biological role of EPS from LAB, as well as their postbiotic action in humans and animals, and to predict the future contribution that they could have on the diet of food animals to improve productivity, animal health status and impact on public health.

Analysis of Transcriptomic Response to SO2 by Oenococcus oeni Growing in Continuous Culture

To successfully complete malolactic fermentation (MLF), Oenococcus oeni must overcome wine stress conditions of low pH, high ethanol, and the presence of SO2. Failure to complete MLF may result in detrimental effects to the quality and stability of the resulting wines. Research efforts to date have focused on elucidating the mechanisms and genetic features that confer the ability to withstand low pH and high ethanol concentrations on O. oeni; however, the responses to SO2 stress are less well defined. This study focused on characterizing the transcriptional response of O. oeni to SO2 challenge during cultivation in a continuous system at wine-like pH (3.5). This experimental design allowed the precise discrimination of transcriptional changes linked to SO2 stress from responses associated with growth stage and cultivation parameters. Differential gene expression analysis revealed major transcriptional changes following SO2 exposure and suggested that this compound primarily interacts with intracellular proteins, DNA, and the cell envelope of O. oeni. The molecular chaperone hsp20, which has a demonstrated function in the heat, ethanol, and acid stress response, was highly upregulated, confirming its additional role in the response of this species to SO2 stress. This work also reports the first nanopore-based complete genome assemblies for O. oeni. IMPORTANCE Malolactic fermentation is an indispensable step in the elaboration of most wines and is generally performed by Oenococcus oeni, a Gram-positive heterofermentative lactic acid bacterium species. While O. oeni is tolerant to many of the wine stresses, including low pH and high ethanol concentrations, it has high sensitivity to SO2, an antiseptic and antioxidant compound regularly used in winemaking. Understanding the physiological changes induced in O. oeni by SO2 stress is essential for the development of more robust starter cultures and methods for their use. This study describes the main transcriptional changes induced by SO2 stress in the wine bacterium O. oeni and provides foundational understanding on how this compound interacts with the cellular components and the induced protective mechanisms of this species.

Biomedical and therapeutic potential of exopolysaccharides by Lactobacillus paracasei isolated from sauerkraut: Screening and characterization

The intention of the study was evaluated for purification and characterization of exopolysaccharides from Lactobacillus paracasei; was isolated from homemade Sauerkraut sample collected from Sivakasi, Tamil Nadu, India, confirmed by biochemical and gene sequencing (16S rRNA). The purification and characterization of exopolysaccharides from candidate bacterium were studied on appearance, solubility of the EPS, carbohydrate estimation, emulsifying activity, sulphate, protein, uronic acid content, FTIR, HPLC and GC-MS analysis. The percentage of elemental carbon, (54.36%) hydrogen (21.74%), nitrogen (9.63%) and sulphur content (18.03%) were recorded in exopolysaccharides. The emulsification index (E24) of EPS was higher in toluene (79.20) and benzene (78.867) supplemented medium. FTIR spectrum of the candidate bacterial EPS confirmed presence of sulphate compounds, carboxyl group, and hydrogen bonded compounds etc. EPS exhibited 76.34% of Total Antioxidant Capacity (TAC), 71.15% of reducing power, 68.65% of Hydrogen Peroxide scavenging activity and also 60.31% DPPH radical scavenging activity. The potential antioxidant properties observed in exopolysaccharides from Lactobacillus paracasei is considered as valuable drugs.

Waste bread recycling as a baking ingredient by tailored lactic acid fermentation

Food-grade waste and side streams should be strictly kept in food use in order to achieve sustainable food systems. At present, the baking industry creates food-grade waste as excess and deformed products that are mainly utilized for non-food uses, such as bioethanol production. The purpose of this study was therefore to explore the potential of waste wheat bread recycling for fresh wheat bread production. Waste bread recycling was assessed without further processing or after tailored fermentation with lactic acid bacteria producing either dextran or β-glucan exopolysaccharides. When non-treated waste bread slurry was added to new bread dough, bread quality (specific volume and softness) decreased with increasing content of waste bread addition. In situ EPS-production (dextran and microbial β-glucan) significantly increased waste bread slurry viscosity and yielded residual fructose or glucose that could effectively replace the sugar added for yeast leavening. Furthermore, fermentation acidified waste bread matrix, thus improving the hygienic safety of the process. Bread containing dextran synthesized in situ by Weissella confusa A16 showed good technological quality. The produced dextran compensated the adverse effect of recycled bread on new bread quality attributes by 12% increase in bread specific volume and 37% decrease in crumb hardness. In this study, a positive technological outcome of the bread containing microbial β-glucan was not detected. The waste bread fermented by W. confusa A16 containing dextran appears to enable safe bread recycling with low acidity and minimal quality loss.

Role of bacterial cell surface sulfhydryl sites in cadmium detoxification by Pseudomonas putida

Understanding bacterial metal detoxification systems is crucial for determining the environmental impacts of metal pollution and for developing advanced bioremediation and water disinfection strategies. Here, we explore the role of cell surface sulfhydryl sites in bacterial detoxification of Cd, using Pseudomonas putida with surface sulfhydryl sites mostly on its EPS molecules as a model organism. Our results show that 5 and 20 ppm Cd in LB growth medium affects the lag phase of P. putida, but not the overall extent of cell growth at stationary phase, indicating that P. putida can detoxify Cd at these concentrations. EXAFS analysis of Cd bound to biomass from the different growth stages indicates that Cd binds to both sulfhydryl and non-sulfhydryl sites, but that the importance of Cd-sulfhydryl binding increases from early exponential to stationary phase. Cell growth is positively correlated to the measured sulfhydryl concentration on different biomass samples, but is independent of the measured non-sulfhydryl binding site concentration on the cell surfaces. Taken together, our results demonstrate that the sulfhydryl binding sites on EPS molecules can play an important role in binding and detoxifying toxic metals, significantly decreasing the bioavailability of the metal by sequestering it away from the bacterial cells.

Multiplex PCR for rapid identification of major lactic acid bacteria genera in cider and other fermented foods

Lactobacillus, Pediococcus, Oenococcus and Leuconostoc are the main Lactic Acid Bacteria (LAB) genera present in cider as they are able to survive this hostile environment. LAB play a significant role in cider quality, for example in the process of malolactic fermentation, even though they can also be involved in spoilage of cider (production of biogenic amines, exopolysaccharides, off-flavours…). In this context a better monitoring of the fermentation process is a matter of interest to guarantee cider quality. In the present study, we designed a genus-specific multiplex PCR for a rapid and simultaneous detection of the four main LAB genera involved in cider production. This multiplex PCR worked equally with purified genomic DNA of bacterial isolates and with colonies directly picked from agar plates. This new PCR method was also successfully extended to wine and dairy isolates, and thus constitutes an effective tool to quickly identify LAB associated with fermented foods. Moreover, many biodiversity studies would also benefit from this fast, cheap and reliable identification method.

Production and Antimicrobial Activity of Nisin Under Enological Conditions

Lactic acid bacteria (LAB) are responsible for the malolactic fermentation of wines, and, therefore, controlling the growth of these bacteria is a key factor for elaborating premium wines. Sulfur dioxide has been traditionally used as an efficient antimicrobial and antioxidant agent, however, nowadays consumers' demand tends toward a reduction of sulfur dioxide levels in wine and other fermented foods. A previous study of our research group had demonstrated the effectiveness of the bacteriocin nisin to inhibit the growth of enological LAB, and its activity had been tested in culture broths. The aim of this study was to investigate the possibility of controlling the growth of bacteria in wine by the use of nisin in combination with sulfur dioxide, and to study nisin production by the natural producer Lactococcus lactis LM29 under enological conditions. Our results showed that L. lactis LM29 produced nisin in the presence of 2 and 4% ethanol (v/v), while higher concentrations of ethanol fully inhibited the production of nisin. We obtained a nisin enriched active extract (NAE) from the cell-free supernatant of a culture of L. lactis LM29 in MRS broth containing 60% (v/v) sterile grape juice, and the extract was fully active in inhibiting the growth of the enological LAB tested by the microtiter method. Moreover, the nisin concentration of the obtained NAE could actually prevent the formation of an undesirable biofilm of LAB strains. Finally, our results of wine ageing under winery conditions showed that the use of 50 mg/L nisin decreased fourfold the concentration of sulfur dioxide required to prevent LAB growth in the wines.

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.

Microorganisms in Fermented Apple Beverages: Current Knowledge and Future Directions

Production of fermented apple beverages is spread all around the world with specificities in each country. 'French ciders' refer to fermented apple juice mainly produced in the northwest of France and often associated with short periods of consumption. Research articles on this kind of product are scarce compared to wine, especially on phenomena associated with microbial activities. The wine fermentation microbiome and its dynamics, organoleptic improvement for healthy and pleasant products and development of starters are now widely studied. Even if both beverages seem close in terms of microbiome and process (with both alcoholic and malolactic fermentations), the inherent properties of the raw materials and different production and environmental parameters make research on the specificities of apple fermentation beverages worthwhile. This review summarizes current knowledge on the cider microbial ecosystem, associated activities and the influence of process parameters. In addition, available data on cider quality and safety is reviewed. Finally, we focus on the future role of lactic acid bacteria and yeasts in the development of even better or new beverages made from apples.

Sulfhydryl Binding Sites within Bacterial Extracellular Polymeric Substances

In this study, the concentration of sulfhydryl sites on bacterial biomass samples with and without extracellular polymeric substances (EPS) was measured in order to determine the distribution of sulfhydryl sites on bacteria. Three different approaches were employed for EPS removal from Pseudomonas putida, and the measured sulfhydryl concentrations on bacterial EPS molecules are independent of the EPS removal protocols used. Prior to EPS removal, the measured sulfhydryl sites within P. putida samples was 34.9 ± 9.5 μmol/g, and no sulfhydryl sites were detected after EPS removal, indicating that virtually all of the sulfhydryl sites are located on the EPS molecules produced by P. putida. In contrast, the sulfhydryl sites within the S. oneidensis samples increased from 32.6 ± 3.6 μmol/g to 51.9 ± 7.2 μmol/g after EPS removal, indicating that the EPS produced by S. oneidensis contained fewer sulfhydryl sites than those present on the untreated cells. This study suggests that the sulfhydryl concentrations on EPS molecules may vary significantly from one bacterial species to another, thus it is crucial to quantify the concentration of sulfhydryl sites on EPS molecules of other bacterial species in order to determine the effect of bacterial EPS on metal cycling in the environment.

Biopolymers from lactic acid bacteria. Novel applications in foods and beverages

Lactic acid bacteria (LAB) are microorganisms widely used in the fermented food industry worldwide. Certain LAB are able to produce exopolysaccharides (EPS) either attached to the cell wall (capsular EPS) or released to the extracellular environment (EPS). According to their composition, LAB may synthesize heteropolysaccharides or homopolysaccharides. A wide diversity of EPS are produced by LAB concerning their monomer composition, molecular mass, and structure. Although EPS-producing LAB strains have been traditionally applied in the manufacture of dairy products such as fermented milks and yogurts, their use in the elaboration of low-fat cheeses, diverse type of sourdough breads, and certain beverages are some of the novel applications of these polymers. This work aims to collect the most relevant issues of the former reviews concerning the monomer composition, structure, and yields and biosynthetic enzymes of EPS from LAB; to describe the recently characterized EPS and to present the application of both EPS-producing strains and their polymers in the fermented (specifically beverages and cereal-based) food industry.

Characterization and upregulation of bifunctional phosphoglucomutase/phosphomannomutase enzyme in an exobiopolymer overproducing strain of Acinetobacter haemolyticus

Several members of the Acinetobacter spp. produce exobiopolymer (EBP) of considerable biotechnological interest. In a previous study, we reported phosphate removal capacity of EBP produced by Acinetobacter haemolyticus. Insertional mutagenesis was attempted to develop EBP-overproducing strains of A. haemolyticus and mutant MG606 was isolated. In order to understand the underlying mechanism of overproduction, the EBP overproducing mutant MG606 was analyzed and compared with the wild type counterpart for its key EBP synthetic enzymes. The EBP produced by MG606 mutant was 650 mg/L compared to 220 mg/L in its wild type counterpart. Significantly high (p<0.05) levels of phosphoglucomutase/phosphomannomutase (PGM/PMM) in MG606 mutant was noted, whereas activities of other enzymes responsible for EBP synthesis showed no significant change (p>0.05). The up-regulation of PGM/PMM expression in mutant was further confirmed by real time reverse transcriptase (RT)-PCR of PGM/PMM transcripts. The optimal conditions for PGM/PMM activity were found to be 35 °C and pH 7.5; PGM/PMM activity was inhibited by ions such as lithium, zinc, nickel. Further, incubation of cells with a PGM inhibitor (lithium) resulted in a concentration-dependent decrease in EBP production further confirming the role of PGM/PMM overexpression in enhanced EBP production by the mutant. Overall the results of our study indicate a key role of PGM/PMM in enhanced EBP production, as evident from enhanced enzyme activity, increased PGM/PMM transcripts and reduction in EBP synthesis by a PGM inhibitor. We envisage a potential exploitation of the insights so obtained to effectively engineer strains of Acinetobacter for overproducing phosphate binding EBP.

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

Strains CUPV261T 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 CUPV261T and CUPV262 was evaluated through RAPD fingerprinting. In addition, a random partial genome pyrosequencing approach was performed on strain CUPV261T in order to compare it with the genome sequence of Lactobacillus vini DSM 20605T and calculate indexes of average nucleotide identity (ANI) between them. Results permit the conclusion that strains CUPV261T and CUPV262 represent a novel species of the genus Lactobacillus , for which the name Lactobacillus sicerae sp. nov. is proposed. The type strain is CUPV261T ( = CECT 8227T = KCTC 21012T).

A specific immunological method to detect and quantify bacterial 2-substituted (1,3)-β-D-glucan

Exopolysaccharides synthesized by lactic acid bacteria have prebiotic properties and contribute to the rheology and texture of fermented foods. Here, we have standardized an immunological method for the specific detection of 2-substituted (1,3)-β-D-glucans. The method allows direct detection and quantification of this exopolysaccharide in culture supernatants containing other mono- and poly-saccharides. Moreover, it allows specific detection of the biomolecules synthesized in vitro in enzymatic reactions. Thus, this method allows the fast identification of producing bacteria, as well as biochemical characterization of the glycosyltransferases responsible for their synthesis.

Exopolysaccharide (EPS) synthesis by Oenococcus oeni: from genes to phenotypes

Oenococcus oeni is the bacterial species which drives malolactic fermentation in wine. The analysis of 50 genomic sequences of O. oeni (14 already available and 36 newly sequenced ones) provided an inventory of the genes potentially involved in exopolysaccharide (EPS) biosynthesis. The loci identified are: two gene clusters named eps1 and eps2, three isolated glycoside-hydrolase genes named dsrO, dsrV and levO, and three isolated glycosyltransferase genes named gtf, it3, it4. The isolated genes were present or absent depending on the strain and the eps gene clusters composition diverged from one strain to another. The soluble and capsular EPS production capacity of several strains was examined after growth in different culture media and the EPS structure was determined. Genotype to phenotype correlations showed that several EPS biosynthetic pathways were active and complementary in O. oeni. Can be distinguished: (i) a Wzy -dependent synthetic pathway, allowing the production of heteropolysaccharides made of glucose, galactose and rhamnose, mainly in a capsular form, (ii) a glucan synthase pathway (Gtf), involved in β-glucan synthesis in a free and a cell-associated form, giving a ropy phenotype to growth media and (iii) homopolysaccharide synthesis from sucrose (α-glucan or β-fructan) by glycoside-hydrolases of the GH70 and GH68 families. The eps gene distribution on the phylogenetic tree was examined. Fifty out of 50 studied genomes possessed several genes dedicated to EPS metabolism. This suggests that these polymers are important for the adaptation of O. oeni to its specific ecological niche, wine and possibly contribute to the technological performance of malolactic starters.

A partial proteome reference map of the wine lactic acid bacterium Oenococcus oeni ATCC BAA-1163

Oenococcus oeni is the main lactic acid bacterium that carries out the malolactic fermentation in virtually all red wines and in some white and sparkling wines. Oenococcus oeni possesses an array of metabolic activities that can modify the taste and aromatic properties of wine. There is, therefore, industrial interest in the proteins involved in these metabolic pathways and related transport systems of this bacterium. In this work, we report the characterization of the O. oeni ATCC BAA-1163 proteome. Total and membrane protein preparations from O. oeni were standardized and analysed by two-dimensional gel electrophoresis. Using tandem mass spectrometry, we identified 224 different spots corresponding to 152 unique proteins, which have been classified by their putative function and subjected to bioinformatics analysis.

Relevance of fucose-rich extracellular polysaccharides produced by Rhizobium sullae strains nodulating Hedysarum coronarium l. legumes

Specific and complex interactions between soil bacteria, known as rhizobia, and their leguminous host plants result in the development of root nodules. This process implies a complex dialogue between the partners. Rhizobia synthesize different classes of polysaccharides: exopolysaccharides (EPS), Kdo-rich capsular polysaccharides, lipopolysaccharides, and cyclic β-(1,2)-glucans. These polymers are actors of a successful symbiosis with legumes. We focus here on studying the EPS produced by Rhizobium sullae bacteria that nodulate Hedysarum coronarium L., largely distributed in Algeria. We describe the influence of the carbon source on the production and on the composition of EPS produced by R. sullae A6 and RHF strains. High-molecular-weight EPS preserve the bacteria from desiccation. The structural characterization of the EPS produced by R. sullae strains has been performed through sugar analysis by gas chromatography-mass spectrometry. The low-molecular-weight EPS of one strain (RHF) has been totally elucidated using nuclear magnetic resonance and quantitative time-of-flight tandem mass spectrometry analyses. An unusual fucose-rich EPS has been characterized. The presence of this deoxy sugar seems to be related to nodulation capacity.

Comparative analysis of production and purification of homo- and hetero-polysaccharides produced by lactic acid bacteria

Lactic acid bacteria (LAB) produce homopolysaccharides (HoPS) and heteropolysaccharides (HePS) with potential functional properties. In this work, we have performed a comparative analysis of production and purification trials of these biopolymers from bacterial culture supernatants. LAB strains belonging to four different genera, both natural as well as recombinant, were used as model systems for the production of HoPS and HePS. Two well characterized strains carrying the gft gene were used for β-glucan production, Pediococcus parvulus 2.6 (P. parvulus 2.6) isolated from cider, and the recombinant strain Lactococcus lactis NZ9000[pGTF] (L. lactis NZ9000[pGTF]). In addition, another cider isolate, Lactobacillus suebicus CUPV225 (L. suebicus CUPV225), and Leuconostoc mesenteroides RTF10 (L. mesenteroides RTF10), isolated from meat products were included in the study. Chemical analysis of the EPS revealed that L. mesenteroides produces a dextran, L. suebicus a complex heteropolysaccharide, and the β-glucan producing-strains the expected 2-substituted (1,3)-β-glucan.

Exploration of phenomena contributing to the diversity of Oenococcus oeni exopolysaccharides

Many food-grade bacteria produce exopolysaccharides (EPS) that may modify the food texture or affect their survival rate during food processing. This is the case of O. oeni, a bacterial species who drives malolactic fermentation in wine. The five strains analyzed in the present study all display both isolated genes dedicated to homopolysaccharide synthesis and gene clusters potentially associated with heteropolysaccharide synthesis. The number of isolated glycosyltransferase gene present and the gene composition of one of the operons change from one strain to the other. The soluble EPS yields and the EPS monomer composition vary depending on the strain and or the medium composition. O. oeni appears as a bacterium able to synthesize both homo and heteropolysaccharides. This unique property has rarely been described. Moreover, the abundance of the genetic determinants associated with EPS metabolism suggests that it is very important for the adaptation of the bacteria to wine.

Beta-1,3-glucanase from Delftia tsuruhatensis strain MV01 and its potential application in vinification

During vinification microbial activities can spoil wine quality. As the wine-related lactic acid bacterium Pediococcus parvulus is able to produce slimes consisting of a β-1,3-glucan, must and wine filtration can be difficult or impossible. In addition, the metabolic activities of several wild-type yeasts can also negatively affect wine quality. Therefore, there is a need for measures to degrade the exopolysaccharide from Pediococcus parvulus and to inhibit the growth of certain yeasts. We examined an extracellular β-1,3-glucanase from Delftia tsuruhatensis strain MV01 with regard to its ability to hydrolyze both polymers, the β-1,3-glucan from Pediococcus and that from yeast cell walls. The 29-kDa glycolytic enzyme was purified to homogeneity. It exhibited an optimal activity at 50°C and pH 4.0. The sequencing of the N terminus revealed significant similarities to β-1,3-glucanases from different bacteria. In addition, the investigations indicated that this hydrolytic enzyme is still active under wine-relevant parameters such as elevated ethanol, sulfite, and phenol concentrations as well as at low pH values. Therefore, the characterized enzyme seems to be a useful tool to prevent slime production and undesirable yeast growth during vinification.

Naturally occurring 2-substituted (1,3)-beta-D-glucan producing Lactobacillus suebicus and Pediococcus parvulus strains with potential utility in the production of functional foods

We have isolated three lactic acid bacteria (Lactobacillus suebicus CUPV221, Pediococcus parvulus CUPV1 and P. parvulus CUPV22) that produced high levels of 2-substituted (1,3)-beta-D-glucans which increased the viscosity of the growth media. The (1,3)-beta-D-glucan consisted of two main molecular species, with masses of approximately 10(7) and 10(4) Da, whose proportions varied among the strains. The three strains survived exposure to saliva and simulated gastric conditions at pH 5, with P. parvulus CUPV22 surviving at pH 3.1, and L. suebicus CUPV221 surviving at pH 1.8. All strains were resistant to pancreatin and bile salts. P. parvulus CUPV22 exhibited the highest adhesion (10.5%) to Caco-2 cells, which decreased to 1.2% after washing the cells. Finally, P. parvulus CUPV22 and L. suebicus CUPV221 induced the production of inflammation-related cytokines by polarized macrophages, and interestingly, L. suebicus stimulated the production of cytokine IL-10. These results indicate that the three strains have potential utility for the production of functional foods.

Probiotic properties of the 2-substituted (1,3)-beta-D-glucan-producing bacterium Pediococcus parvulus 2.6

Exopolysaccharides have prebiotic potential and contribute to the rheology and texture of fermented foods. Here we have analyzed the in vitro bioavailability and immunomodulatory properties of the 2-substituted (1,3)-beta-D-glucan-producing bacterium Pediococcus parvulus 2.6. It resists gastrointestinal stress, adheres to Caco-2 cells, and induces the production of inflammation-related cytokines by polarized macrophages.

Evidence for exopolysaccharide production by Oenococcus oeni strains isolated from non-ropy wines

AIMS

The aim of this study was to assess the exopolysaccharide (EPS) production capacities of various strains of Oenococcus oeni, including malolactic starters and strains recently isolated from wine.

METHODS AND RESULTS

Fourteen O. oeni strains displaying or not (PCR check on genomic DNA) the gtf gene generally associated with beta-glucan formation and ropiness were grown on grape juice medium, dialysed MRS-derived medium or synthetic medium. The soluble polysaccharides (PS) remaining in the culture supernatant were alcohol precipitated, and their concentration was quantified by the phenol-sulfuric method. Most of the O. oeni strains studied produced significant amounts of EPS, independently of their genotype (gtf+ or gtf-). The EPS production was not directly connected with growth and could be stimulated by changing the growth medium composition. The molecular weight distribution analysis and attempts to determine the PS chemical structure suggested that most strains produce a mixture of EPS.

CONCLUSION

Oenococcus oeni strains recently isolated from wine or cultivated for many generations as a malolactic starter are able to produce EPS other than beta-glucan.

SIGNIFICANCE AND IMPACT OF THE STUDY

These EPS may enhance the bacteria survival in wine (advantage for malolactic starters) and may contribute to the wine colloidal equilibrium.

Chemical and rheological properties of the beta-glucan produced by Pediococcus parvulus 2.6

Some physicochemical and rheological properties of the exopolysaccharide (EPS) produced by Pediococcus parvulus 2.6 were examined. Structural characterization by NMR ((1)H and 2D-COSY) showed that the same EPS, a 2-substituted (1,3)-beta-D-glucan, was synthesized irrespective of sugar source used for growth (glucose, fructose, or maltose). The molecular masses of these beta-glucans were always very high (>10(6) Da) and influenced by the culture medium or sugar source. The steady shear rheological experiments showed that all concentrations of the beta-glucan aqueous solutions exhibited a pseudoplastic behavior at high shear rates. Viscoelastic behavior of beta-glucan solutions was determined by dynamic oscillatory analysis. A critical concentration of 0.35% associated with the appearance of entanglements was calculated. The beta-glucan adopts an ordered hydrogen bond dependent helical conformation in neutral and slightly alkaline aqueous solutions, which was partly denatured under more alkaline conditions.

Characterization of gtf, a glucosyltransferase gene in the genomes of Pediococcus parvulus and Oenococcus oeni, two bacterial species commonly found in wine

"Ropiness" is a bacterial alteration in wines, beers, and ciders, caused by beta-glucan-synthesizing pediococci. A single glucosyltransferase, Gtf, controls ropy polysaccharide synthesis. In this study, we show that the corresponding gtf gene is also present on the chromosomes of several strains of Oenococcus oeni isolated from nonropy wines. gtf is surrounded by mobile elements that may be implicated in its integration into the chromosome of O. oeni. gtf is expressed in all the gtf(+) strains, and beta-glucan is detected in the majority of these strains. Part of this beta-glucan accumulates around the cells forming a capsule, while the other part is liberated into the medium together with heteropolysaccharides. Most of the time, this polymer excretion does not lead to ropiness in a model medium. In addition, we show that wild or recombinant bacterial strains harboring a functional gtf gene (gtf(+)) are more resistant to several stresses occurring in wine (alcohol, pH, and SO(2)) and exhibit increased adhesion capacities compared to their gtf mutant variants.