Lactic Acid Bacteria Species Research Articles

Expanding the biodiversity of Oenococcus oeni through comparative genomics of apple cider and kombucha strains

BackgroundOenococcus oeni is a lactic acid bacteria species adapted to the low pH, ethanol-rich environments of wine and cider fermentation, where it performs the crucial role of malolactic fermentation. It has a small genome and has lost the mutS-mutL DNA mismatch repair genes, making it a hypermutable and highly specialized species. Two main lineages of strains, named groups A and B, have been described to date, as well as other subgroups correlated to different types of wines or regions. A third group “C” has also been hypothesized based on sequence analysis, but it remains controversial. In this study we have elucidated the species population structure by sequencing 14 genomes of new strains isolated from cider and kombucha and performing comparative genomics analyses.ResultsSequence-based phylogenetic trees confirmed a population structure of 4 clades: The previously identified A and B, a third group “C” consisting of the new cider strains and a small subgroup of wine strains previously attributed to group B, and a fourth group “D” exclusively represented by kombucha strains. A pair of complete genomes from group C and D were compared to the circularized O. oeni PSU-1 strain reference genome and no genomic rearrangements were found. Phylogenetic trees, K-means clustering and pangenome gene clusters evidenced the existence of smaller, specialized subgroups of strains. Using the pangenome, genomic differences in stress resistance and biosynthetic pathways were found to uniquely distinguish the C and D clades.ConclusionsThe obtained results, including the additional cider and kombucha strains, firmly established the O. oeni population structure. Group C does not appear as fully domesticated as group A to wine, but showed several unique patterns which may be due to ongoing specialization to the cider environment. Group D was shown to be the most divergent member of O. oeni to date, appearing as the closest to a pre-domestication state of the species.

Clustering of Streptococcus thermophilus Strains to Establish a Relation between Exopolysaccharide Characteristics and Gel Properties of Acidified Milk.

In situ produced extracellular polysaccharides (EPS) from lactic acid bacteria are generally known to affect the texture of fermented dairy products; however, the interplay between EPS and product properties is still poorly understood. The aim of this study was to establish a relationship between concentration and properties of EPS, and gel formation of milk analysed by noninvasive Multispeckle Diffusing Wave Spectroscopy. Twenty Streptococcus thermophilus strains were classified with respect to EPS concentration (8–126 mg GE/kg) and ropiness (thread length: 15–80 mm). Five groups identified by cluster analysis demonstrate the high strain-to-strain variability even within one species of lactic acid bacteria. Results from acidification and gelation experiments averaged per cluster indicate that fermentation time and gel stiffness is higher for strains that produce ropy EPS. A further increase in gel stiffness was detected for strains that also produced cell-bound EPS, which underlines the importance of both ropy and cell-bound EPS for improving acid gel properties. The results may be helpful for a proper selection of EPS-producing starter cultures.

Molecular identification and species diversity of the microbiota associated with Soumbara, a traditional fermented food commonly consumed in Cote d’Ivoire

The aim of this study was to investigate the species diversity of microbiota isolated from soumbara, a traditional alkaline-fermented food and the microbial distribution in six major producing regions in Cote d'Ivoire. Ribosomal gene sequencing revealed that the Ivorian soumbara is associated with a wide microbial diversity essentially composed of 10 Bacillus species representing more than 90% of total microbial isolates, 3 species of lactic acid bacteria (2.48%), 2 species of Staphylococcus (1.42%), 8 fungal species (4.61%) and 1.06% of other microorganisms. However, the PCR-RFLP revealed a very weak intraspecific diversity as strains belonging to the same species showed a single restriction profile. Moreover, the microbiota associated with Ivorian soumbara consisted in a core and autochthonous microbiota namely B. subtilis and B. velezensis that were consistently present in samples from all regions studied and an incidental microbiota that was variable through the regions. Among the variable microorganisms, the presence of potential pathogen opportunistic such as Staphylococcus pasteuri, Staphylococcus sciuri and toxinogen species such as B. cytotoxicus and Aspergellus flavus were particularly found. The core microbiota is believed to be involved in the normal process of African locust beans into soumbara and can serve as potential starter whereas the incidental and variable microbiota rather undesirable may be involved in the spoilage or food-born disease. In this study, many species were described for the first time in soumbara, and revealed a new biodiversity of microbiota associated with soumbara in Cote d’Ivoire.

Lactic acid bacteria decrease Salmonella enterica Javiana virulence and modulate host inflammation during infection of an intestinal epithelial cell line.

Salmonella enterica Javiana is a leading cause of severe foodborne Salmonellosis. Despite its emergence as a major foodborne pathogen, little is known of how S. Javiana interacts with intestinal epithelial cells, or of potential methods for ameliorating the bacterial-host interaction. Using cell-based adhesion, invasion and lactate dehydrogenase release assays, we observed an invasive and cytotoxic effect of S. Javiana on intestinal epithelial cells. We assessed the effect of probiotic species of lactic acid bacteria (LAB) on the S. Javiana-host cell interaction, and hypothesized that LAB would reduce S. Javiana infectivity. Salmonella enterica Javiana invasion was significantly impaired in host cells pre-treated with live Lactobacillus acidophilus and Lactobacillus rhamnosus. In addition, pre-exposure of host cells to live L. acidophilus, L. rhamnosus and L. casei reduced S. Javiana-induced cytotoxicity, while heat-killed LAB cultures had no effect on S. Javiana invasion or cytotoxicity. qRT-PCR analysis revealed that S. Javiana exposed to L. acidophilus and L. rhamnosus exhibited reduced virulence gene expression. Moreover, pre-treating host cells with LAB prior to S. Javiana infection reduced host cell production of inflammatory cytokines. Data suggest a potential protective effect of L. acidophilus, L. rhamnosus and L. casei against intestinal epithelial infection and pathogen-induced damage caused by S. Javiana.

Development of a novel selection/counter-selection system for chromosomal gene integrations and deletions in lactic acid bacteria

BackgroundThe underlying mechanisms by which probiotic lactic acid bacteria (LAB) enhance the health of the consumer have not been fully elucidated. Verification of probiotic modes of action can be achieved by using single- or multiple-gene knockout analyses of bacterial mutants in in vitro or in vivo models. We developed a novel system based on an inducible toxin counter-selection system, allowing for rapid and efficient isolation of LAB integration or deletion mutants. The Lactococcus lactis nisin A inducible promoter was used for expression of the Escherichia coli mazF toxin gene as counter-selectable marker.ResultsThe flippase (FLP)/flippase recognition target (FRT) recombination system and an antisense RNA transcript were used to create markerless chromosomal gene integrations/deletions in LAB. Expression of NisR and NisK signalling proteins generated stable DNA integrations and deletions. Large sequences could be inserted or deleted in a series of steps, as demonstrated by insertion of the firefly bioluminescence gene and erythromycin resistance marker into the bacteriocin operons or adhesion genes of Lactobacillus plantarum 423 and Enterococcus mundtii ST4SA.ConclusionsThe system was useful in the construction of L. plantarum 423 and E. mundtii ST4SA bacteriocin and adhesion gene mutants. This provides the unique opportunity to study the role of specific probiotic LAB genes in complex environments using reverse genetics analysis. Although this work focuses on two probiotic LAB strains, L. plantarum 423 and E. mundtii ST4SA, the system developed could be adapted to most, if not all, LAB species.

Interactions between spoilage bacteria in tri-species biofilms developed under simulated meat processing conditions.

The formation of biofilms in the food industry is a major issue, as they are a frequent source of contamination of products, which can result in significant economic losses for processors through spoilage of foods or pose serious health concerns for consumers when foodborne pathogens are present. In this study, experiments were carried out using CDC Biofilm Reactors to produce biofilms on two test surfaces (polystyrene and stainless steel coupons) under a regimen for simulated meat processing conditions (SMPC). This entailed a 12 day regimen of daily cycles of filling the reactors with a meat slurry and letting stand for 16 h, followed by draining and refilling with water for an 8 h period in order to mimic a possible scenario of fluctuating periods of nutrient availability and starvation in a meat processing facility. Strains of Pseudomonas fluorescens, Lactobacillus plantarum and Leuconostoc pseudomesenteroides were used for mono and mixed cultures biofilms as they are relevant spoilage bacteria in the meat processing industry. In monoculture, the viable cell densities (CFU/cm2) of the two lactic acid bacteria species tested were higher for biofilms grown on polystyrene as compared to those obtained on stainless steel, whereas viable cell numbers in P. fluorescens monoculture were surface-independent. Synergistic interactions were demonstrated during growth of multi-species biofilms. Results from experiments where one of the 3 strains was inoculated 24 h before introduction of the other two strains showed increased levels of L. plantarum within biofilms grown on both test surfaces. The model developed here serves as a baseline to study the interactions between potential spoilage bacteria during biofilm development.

Survey on the CRISPR arrays in Lactobacillus helveticus genomes.

Lactobacillus helveticus is a homofermentative thermophilic lactic acid bacteria that is mainly used in the manufacture of Swiss type and long-ripened Italian hard cheeses. In this study, the presence of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) were analysed in 25 L. helveticus genomes and identified in 23 of these genomes. A total of 40 CRISPR loci were identified and classified into five main families based on CRISPR repeats: Ldbu1, Lsal1, Lhel1, Lhel2 and a new repeat family named Lhel3. Spacers had a size between 30 and 40bp whereas repeats have an average size of 30bp, with three longer repeats. The analysis displayed the presence of conserved spacers in 23 of the 40 CRISPR loci. A geographical distribution of L. helveticus isolates with similar CRISPR spacer array profiles were not observed. Based on the presence of the signature protein Cas3, all CRISPR loci belonged to Type I. This analysis demonstrated a great CRISPR array variability within L. helveticus, which could be a useful tool for genotypic strain differentiation. A next step will be to understand the possible role of CRISPR/Cas system for the resistance of L. helveticus to phage infection. SIGNIFICANCE AND IMPACT OF THE STUDY: Lactobacillus helveticus, a lactic acid bacteria species widely used as starter culture in the dairy industry has recently also gained importance as health-promoting culture in probiotic and nutraceutical food products. The CRISPR/Cas system, a well-known molecular mechanism that provides adaptive immunity against exogenous genetic elements such as bacteriophages and plasmids in bacteria, was recently found in this species. In this study, we investigated the presence and genetic heterogeneity of CRISPR loci in 25 L. helveticus genomes. The results presented here represent an important step on the way to manage phage resistance, plasmid uptake and genome editing in this species.

Dense tracking of the dynamics of the microbial community and chemicals constituents in spontaneous wheat sourdough during two months of backslopping

Wheat sourdough is a common traditional fermented food that is produced worldwide. However, product quality of spontaneous sourdough is not easy to control because it depends on natural fermentation and backslopping, about which little is known, notably after ten backslopping steps. To this end, we tracked the spontaneous fermentation of three sourdoughs made from wheat flours during 32 backslopping steps for 60 days. At 24 time points, the microbial community was analyzed by both culture-dependent and culture-independent methods and its chemical constituents were assessed. Dynamic changes were observed in the microbial community, which showed a common succession pattern among the three sourdoughs at the bacterial family level and differences at the species level. The bacterial communities evolved through three phases that were driven by different groups of lactic acid bacteria (LAB) species. The dynamism among the metabolites also differed, depending on the species composition of the LAB and yeast communities. In one sourdough, the growth of Saccharomyces cerevisiae was detected along with a concentration of increased ethanol, while in the other two sourdoughs, Wickerhamomyces anomalus was detected without ethanol production. Regarding the LAB communities, two sourdoughs were eventually co-dominated by Lactobacillus plantarum and L. brevis, while the other sourdough was eventually dominated solely by the heterolactic fermentative bacterium Lactobacillus fermentum, and ethanol was produced at the same level as lactic acid. Further research is needed to determine the bacterial and yeast species involved in the fermentation of sourdough, to help improve the design and quality control of the final product.

Shotgun Metagenomics of a Water Kefir Fermentation Ecosystem Reveals a Novel Oenococcus Species.

Water kefir is a fruity, sour, slightly alcoholic and carbonated beverage, which is made by fermentation of an aqueous sucrose solution in the presence of dried figs and water kefir grains. These polysaccharide grains contain lactic acid bacteria (LAB), yeasts, and sometimes bifidobacteria and/or acetic acid bacteria, which consume sucrose to produce exopolysaccharides, lactic acid, acetic acid, ethanol, and carbon dioxide. Shotgun metagenomic sequencing was used to examine the microbial species diversity present at two time points during water kefir fermentation in detail, both in the water kefir liquor and on the water kefir grains, hence representing four samples. Lactobacillus harbinensis, Lactobacillus hilgardii, Lactobacillus nagelii, Lactobacillus paracasei, and a Lactobacillus species similar to Lactobacillus hordei/mali were present in the water kefir examined, along with Bifidobacterium aquikefiri and two yeast species, namely Saccharomyces cerevisiae and Dekkera bruxellensis. In addition, evidence for a novel Oenococcus species related to Oenococcus oeni and Oenococcus kitaharae was found. Its genome was derived from the metagenome and made available under the name of Candidatus Oenococcus aquikefiri. Through functional analysis of the four metagenomic data sets, it was possible to link the production of lactic acid, acetic acid, ethanol, and carbon dioxide to subgroups of the microbial species found. In particular, the production of mannitol from fructose was linked to L. hilgardii, Candidatus O. aquikefiri, and B. aquikefiri, whereas glycerol production was associated with S. cerevisiae. Also, there were indications of cross-feeding, for instance in the case of amino acid supply. Few bacterial species could synthesize a limited number of cofactors, making them reliant on the figs or S. cerevisiae. The LAB species in turn were found to be capable of contributing to water kefir grain growth, as dextransucrase-encoding genes were attributed to L. hilgardii, L. hordei/mali, and Candidatus O. aquikefiri.

Anti-herpetic activity exopolysaccharides produced by different species of lactic acid bacteria

In the present work, it was shown that, in non-toxic concentrations, all EPSs which were isolated from lactic acid bacteria have significant anti-HSV-1 activity affecting various stages of the virus reproduction. It was demonstrated that the use of ESPs leads to the normalization of the life cycle of cells infected with the herpes simplex virus to the level of uninfected cells. It was found that EPS 26a produced by Lactobacillus sp. possesses multiple antiviral effects as it exhibits virucidal activity, blocks adsorption, penetration of the virus into cells and the release of viruses, and reduces the infectious titer of herpes simplex virus by 97-99%, indicating its considerable anti-herpetic activity.

Uncovering carbohydrate metabolism through a genotype-phenotype association study of 56 lactic acid bacteria genomes

Owing to their unique potential to ferment carbohydrates, both homo- and heterofermentative lactic acid bacteria (LAB) are widely used in the food industry. Deciphering the genetic basis that determine the LAB fermentation type, and hence carbohydrate utilization, is paramount to optimize LAB industrial processes. Deep sequencing of 24 LAB species and comparison with 32 publicly available genome sequences provided a comparative data set including five major LAB genera for further analysis. Phylogenomic reconstruction confirmed Leuconostoc and Pediococcus species as independently emerging from the Lactobacillus genus, within one of the three phylogenetic clades identified. These clades partially grouped LABs according to their fermentation types, suggesting that some metabolic capabilities were independently acquired during LAB evolution. In order to apply a genome-wide association study (GWAS) at the multigene family level, utilization of 49 carbohydrates was also profiled for these 56 LAB species. GWAS results indicated that obligately heterofermentative species lack 1-phosphofructokinase, required for d-mannose degradation in the homofermentative pathway. Heterofermentative species were found to often contain the araBAD operon, involved in l-arabinose degradation, which is important for heterofermentation. Taken together, our results provide helpful insights into the genetic determinants of LAB carbohydrate metabolism, and opens for further experimental research, aiming at validating the role of these candidate genes for industrial applications.

Modulation of the intestinal microbiota of dogs by kefir as a functional dairy product

Kefir is a traditional dairy product with multiple probiotic characteristics derived from its associated microorganisms, including more than 50 species of lactic acid bacteria and yeast. For centuries, many people have produced kefir for human consumption; its consumption and potential role as a probiotic supplement in companion animals have never been tested. The present study explored the potential application of kefir as a probiotic supplement for dogs. Kefir was orally administered to healthy adult dogs (n = 6) for 2 wk. On d 0 and 14 (before and after kefir consumption, respectively), gut microbiota was analyzed comprehensively using quantitative PCR and 16S rDNA amplicon-based community analysis using fresh fecal samples. The 16S rDNA amplicon-based community analysis showed that the relative abundance of the phylum Fusobacteria was significantly decreased after kefir consumption. Furthermore, the relative abundance of the families Prevotellaceae, Selenomonadaceae, and Sutterellaceae increased significantly, whereas that of the families Clostridiaceae, Fusobacteriaceae, and Ruminococcaceae decreased significantly. The quantitative PCR assay showed that kefir consumption significantly increased the population of lactic acid bacteria and the lactic acid bacteria:Enterobacteriaceae ratio and significantly decreased the Firmicutes:Bacteroidetes ratio. In summary, 2-wk kefir administration successfully modified the gut microbiota without causing any clinically evident adverse effects. Therefore, kefir could be further developed as a novel probiotic food supplement for dogs to improve the quality of life of dogs.

Novel solid-state fermentation of bee-collected pollen emulating the natural fermentation process of bee bread

Structure of lactic acid bacteria biota in ivy flowers, fresh bee-collected pollen (BCP), hive-stored bee bread, and honeybee gastrointestinal tract was investigated. Although a large microbial diversity characterized flowers and fresh BCP, most of lactic acid bacteria species disappeared throughout the bee bread maturation, giving way to Lactobacillus kunkeei and Fructobacillus fructosus to dominate long stored bee bread and honeybee crop. Adaptation of lactic acid bacteria was mainly related to species-specific, and, more in deep, to strain-specific features. Bee bread preservation seemed related to bacteria metabolites, produced especially by some L. kunkeei strains, which likely gave to lactic acid bacteria the capacity to outcompete other microbial groups. A protocol to ferment BCP was successfully set up, which included the mixed inoculum of selected L. kunkeei strains and Hanseniaspora uvarum AN8Y27B, almost emulating the spontaneous fermentation of bee bread. The strict relationship between lactic acid bacteria and yeasts during bee bread maturation was highlighted. The use of the selected starters increased the digestibility and bioavailability of nutrients and bioactive compounds naturally occurring in BCP. Our biotechnological protocol ensured a product microbiologically stable and safe. Conversely, raw BCP was more exposed to the uncontrolled growth of yeasts, moulds, and other bacterial groups.

Liquid and firm sourdough fermentation: microbial robustness and interactions during consecutive backsloppings

This study investigated the establishment of wheat stable sourdoughs, both in liquid (dough yield = 330) and firm (dough yield = 154) conditions, by inoculating 5 strains of different lactic acid bacteria species together with either a Saccharomyces cerevisiae or a Candida milleri strain. Real propagation cycles, consisting of ten refreshments, were simulated to assess the behaviour and robustness of the microorganisms. The results indicated stable microbial communities from seventh backslopping in all the tested conditions, with some differences among the strains. Lactobacillus farciminis Lf19 proved to be the most competitive strain, maintaining high concentrations throughout the refreshments at different dough yield, while Lactobacillus rossiae Lr9 resulted the less performing strain. Due to the longer refreshment time (24h instead of 6h) and to the presence of Saccharomyces cerevisiae, Lactobacillus sanfranciscensis Ls51 was probably affected by the maltose depletion in liquid condition. At sourdoughs stability, the main technological characteristics (pH, total titratable acidity, fermentation quotient) were in agreement with those reported for mature sourdoughs. Overall, this study evaluated the effect of modifying some parameters (dough yield, refreshment time, associated yeast, etc.) on microbial composition and on sourdough main features, to select the most suitable sourdough technology to be used.

Studies on Lactic Acid Bacteria Isolate Sr 13 From Bali Cattle Gastric

Lactic acid bacteria (LAB) is a generic term for bacteria that ferment lactose and produce lactic acid as its main product. In general, lactic acid bacteria belonging to Gram positive bacteria, negative catalase, does not form spores, have no cytochrome, aerotolerant, anaerobic to microaerophilic, require complex nutrients such as amino acids, vitamins (B1, B6, B12 and biotin), purine, pyrimidine. This study aims to determine the species of lactic acid bacteria (LAB) from isolate SR13 isolated from rumen liquid of bali cattle. The identification was started by cultivation of isolate on de Man, Rogosa, Sharpe (MRS) medium with anaerobic condition, confirmation of isolates by Gram staining and catalase test, and finally identificion of species by using conventional test and 50CH API test kit. The results of study showed, the isolate of LAB SR 13 was detected asPediococcus/Enterococcus, moreover, identification by using 50CH Api test kit showed as Pediococcus pentosaceus 2

Enterococcus faecium L-15 Cell-Free Extract Improves the Chondrogenic Differentiation of Human Dental Pulp Stem Cells

Hyaline cartilage is a tissue of very low regenerative capacity because of its histology and limited nutrient supply. Cell-based therapies have been spotlighted in the regeneration of damaged cartilage. Dental pulp stem cells (DPSCs) are multipotent and are easily accessible for therapeutic purposes. In human gastrointestinal tracts, Enterococcus faecium is a naturally occurring commensal species of lactic acid bacteria. In this work, the human DPSCs were differentiated into chondrocytes using a chondrogenic differentiation medium with or without L-15 extract. We observed that chondrogenic differentiation improved in an E. faecium L-15 extract (L-15)-treated DPSC group via evaluation of chondrogenic-marker mRNA expression levels. In particular, we found that L-15 treatment promoted early-stage DPSC differentiation. Cells treated with L-15 were inhibited at later stages and were less likely to transform into hypertrophic chondrocytes. In L-15-treated groups, the total amount of cartilage extracellular matrix increased during the differentiation process. These results suggest that L-15 promotes chondrogenic differentiation, and that L-15 may be used for cartilage repair or cartilage health supplements. To our knowledge, this is the first report demonstrating the beneficial effect of L-15 treatment on chondrogenic differentiation.

Reliable identification of lactic acid bacteria by targeted and untargeted high-resolution tandem mass spectrometry

Probiotic lactic acid bacteria (LAB) are generally employed in food industry because they contribute to nutritional value of fermented foods. Although knowledge of LAB composition is of high relevance for various industrial and biotechnological applications, the comprehensive identification of LAB species is sometimes technically challenging. Recently, MALDI-TOF MS-based methodologies for bacteria detection/identification in clinical diagnostics and agri-food proved to be an attractive strategy, complementary to traditional techniques for their sensitivity and specificity.In this study, we propose, for the first time, a novel methodology based on high resolution nano-LC-ESI-MS/MS for LAB identification at genus, species and sub-species level by using the sequence regions 33–52 and 72–82 of the S16 ribosomal protein as proteotypic peptide markers.The developed methodology was then applied to the analyses of buffalo and bovine whey starter cultures, thus assessing the applicability of the approach for the detection of LAB also in complex matrices.

Aroma formation in retentostat co-cultures of Lactococcus lactis and Leuconostoc mesenteroides

Lactococcus lactis subsp. lactis biovar diacetylactis and Leuconostoc mesenteroides are considered to be the main aroma producers in Dutch-type cheeses. Both species of lactic acid bacteria were grown in retentostat mono- and co-cultures to investigate their interaction at near-zero growth rates and to determine if co-cultivation enhances the aroma complexity compared to single species performance. During retentostat mono-cultures, the growth rates of both species decreased to less than 0.001 h−1 and a large fraction of the cells became viable but not culturable. Compared to Lc. mesenteroides, L. lactis reached a 3.4-fold higher biomass concentration caused by i) a higher ATP yield on substrate, ii) a higher biomass yield on ATP and iii) a lower maintenance requirement (mATP). Dynamic models estimated that the mATP of both species decreased approximately 7-fold at near-zero growth rates compared to high growth rates. Extension of these models by assuming equal substrate distribution resulted in excellent prediction of the biomass accumulation in retentostat co-cultures with L. lactis dominating (100:1) as observed in ripened cheese. Despite its low abundance (∼1%), Lc. mesenteroides contributed to aroma production in co-cultures as indicated by the presence of all 5 specific Lc. mesenteroides compounds. This study provides insights in the production of cheese aroma compounds outside the cheese matrix by co-cultures of L. lactis and Lc. mesenteroides, which could be used as food supplements in dairy or non-dairy products.

Label-free quantitative proteomic analysis reveals the lifestyle of Lactobacillus hordei in the presence of Sacchromyces cerevisiae

Water kefir is a fermented beverage, which is traditionally prepared from sucrose, kefir grains, dried or fresh fruits, and water. L. hordei and S. cerevisiae are isolated as predominant and stable species of lactic acid bacteria and yeasts, respectively. In this study we demonstrate that label free quantitative proteomics is useful to study microbial interaction along the response of co-cultivated L. hordei TMW 1.1822 in the presence of S. cerevisiae TMW 3.221 as compared with their single cultures in a water kefir model. It is shown and L. hordei responds to S. cerevisiae in many respects revealing a mutualistic relationship. The data suggest that L. hordei responds to the presence of S. cerevisiae with adjustment of intracellular redox reactions controlled of proteins, which are part of Rex regulons and proteins involved in the glycolytic pathway and energy fermentation. An NADH, H+-driven metabolic switch to preferential production of butanediol instead of acetate or lactate, and up-regulation of arginine deiminase, alleviated acid stress and concomitantly protected S. cerevisiae against an acidic environment, which L. hordei generated in single culture. Moreover, the data suggest that the presence of S. cerevisiae in the nitrogen and fatty acids limited environment of the water kefir facilitated and improved the growth of L. hordei by delivering gluconate, fructose, amino acids, fatty acids or substrates for their biosynthesis. Up-regulation of the OppABCDF peptide transport and enzymes involved in amino acid metabolism indicates enhanced peptide uptake, as well as cross-feeding of L. hordei by glutamine, glutamate, histidine, tryptophan, methionine, proline, tryptophan delivered by S. cerevisiae.

Fermented Portulaca oleracea L. Juice: A Novel Functional Beverage with Potential Ameliorating Effects on the Intestinal Inflammation and Epithelial Injury.

P. oleracea L. contains high level of nutrients and biologically active compounds. Recently, lactic fermentation has been proposed as a biotechnological option to enrich the profile of biogenic compounds of Portulaca oleracea L. puree. This study investigated the capability of fermentation by selected lactic acid bacteria to enhance the restoring features of Portulaca oleracea juice towards intestinal inflammation and epithelial injury. Lactic acid fermentation markedly increased the total antioxidant capacity of P. oleracea juice, preserved the inherent levels of vitamins C, A, and E, and increased the bioavailability of the level of vitamin B2 and that of phenolics. The effects of fermented P. oleracea juice on a Caco-2 cell line were investigated using an in vitro model closest to the in vivo conditions. Fermented P. oleracea juice strongly decreased the levels of pro-inflammatory mediators and reactive oxygen species. It also counteracted the disruption of the Caco-2 cell monolayers treated with the inflammatory stimulus. We used a diversified spectrum of lactic acid bacteria species, and some effects appeared to be strains- or species-specific. Fermentation with Lactobacillus kunkeei B7 ensured the best combination for the content of bioactive compounds and the ability to counteract the intestinal inflammation and epithelial injury.