Determination of survival, identity and stress resistance of probiotic bifidobacteria in bio-yoghurts

Delivery of Probiotic-Loaded Microcapsules in the Gastrointestinal Tract: A Review

Probiotics are live microorganisms that inhabit the gastrointestinal tract and confer health benefits to consumers. However, a sufficient number of viable probiotic cells must be delivered to the specific site of interest in the gastrointestinal tract to exert these benefits. Enhanced viability and tolerance to sublethal gastrointestinal stress can be achieved using appropriate coating materials and food matrices for orally consumed probiotics. The release mechanism and interaction of probiotic microcapsules with the gastrointestinal tract have been minimally explored in the literature to date. To the authors' knowledge, no review has been published to discuss the nature of release and the challenges in the targeted delivery of probiotics. This review addresses gastrointestinal-related complications in the formulation of targeted delivery and controlled release of probiotic strains. It investigates the impacts of environmental stresses during the transition stage and delivery to the target region in the gastrointestinal tract. The influence of factors such as pH levels, enzymatic degradation, and redox conditions on the release mechanisms of probiotics is presented. Finally, the available methods to evaluate the efficiency of a probiotic delivery system, including in vitro and in vivo, are reviewed and assessed. The paper concludes with a discussion highlighting the emerging technologies in the field and emphasising key areas in need of future study.

Characterization of a Bifidobacterium animalis subsp. lactis reference strain based on ecology and transcriptomics

Bifidobacteria are recognized as health-promoting bacteria that reside in the human gut, helping in the digestion of fiber, preventing infections, and producing essential compounds like vitamins. To date, Bifidobacterium animalis subsp. lactis, together with Bifidobacterium adolescentis, Bifidobacterium bifidum, Bifidobacterium breve, and Bifidobacterium longum, represents one of the species that are used as probiotic bacteria. Despite the extensive and detailed scientific research conducted on this microbial taxon, the molecular mechanisms by which B. animalis subsp. lactis exerts health benefits to its host are still largely unknown. Thus, we dissected the genetic repertoire and phylogenetic relationship of 162 strains of B. animalis subsp. lactis to select a representative reference strain of this taxon suitable for investigating its interaction with the host. The B. animalis subsp. lactis PRL2013 strain, which was isolated by a mucosal sample of a healthy adult, was chosen as the reference of the monophyletic cluster of human origin and revealed a greater adhesion index than that observed for another B. animalis subsp. lactis strain used in the industry as a probiotic supplement. Transcriptomics analyses of PRL2013 strain, when exposed to human cell monolayers, revealed 291 significantly upregulated genes, among which were found genes predicted to encode extracellular structures that may directly interact with human cells, such as extracellular polymeric substances, wall teichoic acids, and pili.

IMPORTANCE

To date, many Bifidobacterium animalis subsp. lactis strains have been isolated from human fecal samples. However, their presence in these samples does not necessarily suggest an ability to colonize the human gut. Furthermore, probiotics of non-human origin may not effectively interact with the gut epithelium, resulting in transient bacteria of the gut microbiota. In vitro experiments with human cells revealed that B. animalis subsp. lactis PRL2013, an autochthonous member of the human gut, shows colonization capability, leading to future applications in functional foods.

Lactic acid bacteria viability in different refrigerated food matrices: a systematic review and Meta‑analysis

The aim of this systematic review and meta-analysis was to determine which variables affect the viability of lactic acid bacteria (LAB) added to different types of refrigerated foods during the first 28 days. Scopus, ScienceDirect, PubMed and Cochrane Central Register of Reviews databases were searched from 1997 to April 2022. A total of 278 studies, which showed randomized and controlled experiments published in peer reviewed journals, were included. The viability of LAB in different moments during the storage process was synthesized as mean point estimate (MPE) via random-effects meta-analyses and the effect of multiple factors on the LAB´s viability was evaluated by multiple meta-regression. The meta-analysis showed that the decrease in LAB viability will be more abrupt the greater the initial dose. The physical structure of food may influence bacterial viability. Fruit was the type of product that most quickly lost viability. Co-culture of two or more species did not affect viability. Preservation methods had an unfavorable effect and prebiotics had a beneficial effect on bacterial viability. Viability was genus dependent. The data obtained in this study provide an overview of the factors to be taken into account for the design of new foods.

Exploratory Study for Probiotic Enrichment of a Sea Fennel (Crithmum maritimum L.) Preserve in Brine

Considering the increasing consumer demand for vegan and vegetarian health foods, different vegetables have been already exploited to produce non-dairy probiotic foods. In addition to being rich in bioactive compounds, sea fennel (Crithmum maritimum L.), also known as rock samphire, represents a valuable candidate in the production of probiotic-enriched foods, and, to the authors' knowledge, it has not yet been explored as carrier for probiotics. Hence, the present study was aimed at evaluating the survival of a commercially available probiotic formulation, SYNBIO^®, and Lactiplantibacillus plantarum IMC 509 in an artificially acidified, pasteurized sea fennel preserve in brine during a refrigerated storage of 44 days. Despite slight reductions in the microbial loads, at the end of the storage, both the probiotic formulations showed loads higher than 7.0 Log CFU g^-1 of sea fennel or mL^-1 of brine, above the recommended administration dose to exert beneficial health effects. Thus, acidified sea fennel sprouts in brine represent a potential vehicle for probiotics delivery to humans.

Designing food for the elderly: the critical impact of food structure

Ageing is an unavoidable progressive process causing many changes of the individual life. However, if faced in an efficient way, living longer in a healthy status could be an opportunity for all. In this context, food consumption and dietary patterns are pivotal factors in promoting active and healthy ageing. The development of food products tailored for the specific needs of the elderly might favour the fulfilment of nutritionally balanced diets, while reducing the consequences of malnutrition. To this aim, the application of a food structure design approach could be particularly profitable, being food structure responsible to the final functionalities of food products. In this narrative review, the physiological changes associated to food consumption occurring during ageing were firstly discussed. Then, the focus shifted to the possible role of food structure in delivering target functionalities, considering food acceptability, digestion of the nutrients, bioactive molecules and probiotic bacteria.

Mango Pectic Oligosaccharides: A Novel Prebiotic for Functional Food

Prebiotics are functional food ingredients that assist probiotic growth and render many other health benefits. Mango peel is the biomass of the processing industry and has recently been value-added as a dietary fiber pectin. Besides its general use as a food additive, mango peel pectin (MPP) is partially hydrolyzed by pectinase to obtain pectic oligosaccharides (POSs) that have recently gained attention as novel prebiotic products and in medical research. This review describes probiotic candidates responsible for the digestion of pectin derivatives and the advantages of POSs as functional additives and their current best retrieval options. Mango pectic oligosaccharide (MPOS) recovery from low methoxyl MPP from mango with prebiotic performance both in vivo and in vitro environments is discussed. Current research gaps and potential developments in the field are also explored. The overall worthiness of this article is the potential use of the cheap-green food processing bioresource for high-value components.

Role of prebiotics in enhancing the function of next-generation probiotics in gut microbiota

With the development of high-throughput DNA sequencing and molecular analysis technologies, next-generation probiotics (NGPs) are increasingly gaining attention as live bacterial therapeutics for treatment of diseases. However, compared to traditional probiotics, NGPs are much more vulnerable to the harsh conditions in the human gastrointestinal tract, and their functional mechanisms in the gut are more complex. Prebiotics have been confirmed to play a critical role in improving the function and viability of traditional probiotics. Defined as substrates that are selectively utilized by host microorganisms conferring a health benefit, prebiotics are also important for NGPs. This review summarizes potential prebiotics for use with NGPs and clarifies their characteristics and functional mechanisms. Then we particularly focus on illustrating the protective effects of various prebiotics by enhancing the antioxidant capacity and their resistance to digestive fluids. We also elucidate the role of prebiotics in regulating anti-bacterial effects, intestinal barrier maintenance, and cross-feeding mechanisms of NPGs. With the expanding range of candidate NGPs and prebiotic substrates, more studies need to be conducted to comprehensively elucidate the interactions between prebiotics and NGPs outside and inside hosts, in order to boost their nutritional and healthcare applications.

Probiotic Sheep Milk Ice Cream with Inulin and Apple Fiber

The aim of the study was to assess the effect of the addition of inulin and the replacement of part of the inulin with apple fiber on the physicochemical and organoleptic properties of ice cream. Moreover, the survival of Bifidobacterium animalis ssp. Lactis Bb-12 and Lactobacillus rhamnosus was studied in sheep milk ice cream. There was no effect of the apple fiber and the type of bacteria on the number of bacteria in the probiotics after fermentation. As a result of freezing, in the mixture containing Bifidobacterium animalis ssp. Lactis Bb-12, there was a significant reduction in the bacteria from 0.39 log cfu g^-1 to 0.46 log cfu g^-1. In all of the ice cream on the 21st day of storage, it exceeded 10 log cfu g^-1, which means that the ice cream retained the status of a probiotic product. The Lactobacillus rhamnosus ice cream showed a lower yellow color compared to the Bifidobacterium Bb-12 ice cream. The overrun of the sheep's milk ice cream was within the range of 78.50% to 80.41%. The appearance of the sheep's milk ice cream is influenced significantly by the addition of fiber and the type of bacteria and the interaction between the type of bacteria and the addition of fiber, and storage time and fiber.

Mining indigenous honeybee gut microbiota for Lactobacillus with probiotic potential

The present study was done to explore the diversity of lactic acid bacteria (LAB) associated with the gastrointestinal tract (GIT) of honeybee species endemic to northeastern Pakistan. Healthy worker bees belonging to Apis mellifera, A. dorsata, A. cerana and A. florea were collected from hives and the surroundings of a major apiary in the region. The 16S rRNA amplicon sequencing revealed a microbial community in A. florea that was distinct from the others in having an abundance of Lactobacillus and Bifidobacteria. However, this was not reflected in the culturable bacteria obtained from these species. The isolates were characterized for safety parameters, and 20 LAB strains deemed safe were evaluated for resistance to human GIT stresses like acid and bile, adhesion and adhesiveness, and anti-pathogenicity. The five most robust strains, Enterococcus saigonensis NPL780a, Lactobacillus rapi NPL782a, Lactobacillus kunkeei NPL783a, and NPL784, and Lactobacillus paracasei NPL783b, were identified through normalized Pearson (n) principal components analysis (PCA). These strains were checked for inhibition of human pathogens, antibiotic resistance, osmotic tolerance, metabolic and enzymatic functions, and carbohydrate utilization, along with antioxidative and cholesterol-removing potential. The findings suggest at least three strains (NPL 783a, 784 and 782a) as candidates for further in vitro and in vivo investigations of their potential health benefits and application as novel probiotic adjuncts.

Design and optimization of a probiotic tablet for gastrointestinal tolerance by a simplex-centroid mixture

In this study, a simplex-centroid mixture design using design of experiment (DOE) software was implemented to evaluate the effect of biopolymers as excipients, which are hydroxypropyl methylcellulose, and alginate, on the gastrointestinal tolerance of probiotic tablet containing Saccharomyces boulardii. Microbial viability and dissolution time were used to evaluate the ideal formulation made using 39.01% carboxymethylcellulose and 60.99% alginate as excipients, which protected the probiotics from the acidic condition in the stomach with good dissolution time. The formulated probiotic tablet is more stable in terms of viability when stored at 4 °C compared to room temperature. However, the viability remains above 10⁶ CFU/tablet after six months of storage at room temperature. This study shows that the simplex-centroid mixture design is valid and can be used to formulate probiotic tablets that possess gastrointestinal tolerance. This study can lead to the development of commercial production of probiotic yeast tablets with gastrointestinal tolerance.

Probiotic Properties of a Lactobacillus fermentum Isolated from New-born Faeces

Lactic acid bacteria (LAB) have been demonstrated to have roles in many applications, ranging from lowering of cholesterol to immunological development. In this study, Lactobacillus fermentum was isolated from a new-born's faeces and its genotypic and probiotic characterizations were performed. Our results showed that the survival rate of isolated Lactobacillus fermentum was 39.39% at pH 2 and 81.34% in the stimulated gastric juice at pH 3. It also digested bile salts. Its surface hydrophobicity was found to be 57.59% in n-hexane. These findings indicated that the isolate can be a good probiotic candidate.

Bacterial survival and adhesion for formulating new oral probiotic foods

Probiotics are defined as live microorganisms, which, when administered in adequate amounts, confer health benefits to the host. Traditionally, probiotic food research has heavily focused on the genera Bifidobacteria and Lactobacilli, along with their benefits for gut health. Recently with the identification of new probiotic strains specifically intended for oral health applications, the development of probiotic foods for oral health benefits has garnered interest, with a renewed focus on identifying new food formats for delivering probiotics. The development of novel oral probiotic foods is highly complex, as the composition of a food matrix dictates: (1) bacterial viability during production and shelf life and (2) how bacteria partition with components within a food matrix and subsequently adhere to oral cavity surfaces. At present, virtually no information is available on oral probiotic strains such as Streptococcus salivarius; specifically, how orally-derived strains survive under different food parameters. Furthermore, limited information exists on the partition behavior of probiotics with food components, governed by physico-chemical interactions and adhesion phenomena. This review aspires to examine this framework by providing a foundation with existing literature related to the common probiotic genera, in order to inform and drive future attempts of designing new oral probiotic food formats.

A successful history: probiotics and their potential as antimicrobials

Introduction: Probiotics are living, non-pathogenic microorganisms (bacteria) that enter through diet in the human body, live during their passage through the gastrointestinal (GI) tract and are beneficial to health. They have become popular in recent years as a way of improving human health through nutrition. This review aims to discuss the efficacy of probiotics for the supportive therapy of certain clinical conditions, especially infectious diseases, as reported in a number of studies, even though some concerns about their safety still remain. Areas covered: This paper will review the history of probiotics, from ancient ages to date, and the evolution of their use in clinical practice. The study is based on both personal professional experience of the authors and a comprehensive literature analysis, including old documents from libraries, searching the related biological and clinical data on Scopus, Web of Science, PubMed, EMBASE, also using the 'cited by' and 'similar articles' options available in PubMed. Expert opinion: Not all researchers agree about the safety and real efficacy of probiotics in common conditions, especially infective diseases. However, the use of probiotics for clinical conditions that may be improved by consumption of these dietary supplements should be considered as a possible supportive therapy in select patients.

Probiotics in Food Systems: Significance and Emerging Strategies Towards Improved Viability and Delivery of Enhanced Beneficial Value

Preserving the efficacy of probiotic bacteria exhibits paramount challenges that need to be addressed during the development of functional food products. Several factors have been claimed to be responsible for reducing the viability of probiotics including matrix acidity, level of oxygen in products, presence of other lactic acid bacteria, and sensitivity to metabolites produced by other competing bacteria. Several approaches are undertaken to improve and sustain microbial cell viability, like strain selection, immobilization technologies, synbiotics development etc. Among them, cell immobilization in various carriers, including composite carrier matrix systems has recently attracted interest targeting to protect probiotics from different types of environmental stress (e.g., pH and heat treatments). Likewise, to successfully deliver the probiotics in the large intestine, cells must survive food processing and storage, and withstand the stress conditions encountered in the upper gastrointestinal tract. Hence, the appropriate selection of probiotics and their effective delivery remains a technological challenge with special focus on sustaining the viability of the probiotic culture in the formulated product. Development of synbiotic combinations exhibits another approach of functional food to stimulate the growth of probiotics. The aim of the current review is to summarize the strategies and the novel techniques adopted to enhance the viability of probiotics.

Survival and Behavior of Encapsulated Probiotics (Lactobacillus plantarum) in Calcium-Alginate-Soy Protein Isolate-Based Hydrogel Beads in Different Processing Conditions (pH and Temperature) and in Pasteurized Mango Juice

Hybrid alginate-soy protein isolate-based hydrogel beads were prepared and evaluated to enhance the survival of the encapsulated probiotics (Lactobacillus plantarum) during heat processing to incorporate in mango juice. The solutions of sodium alginate-soy protein isolate (SA-SPI) with probiotic cells were dropped into the gelation bath containing calcium chloride (3% w/v) solution to develop various types of hydrogel beads. The level of survival of probiotics in encapsulated beads under acidic conditions (pH 2, 3, and 6.5) and bile salt (0.5 and 1.0% w/v) was evaluated. The survival of the encapsulated probiotics to thermal processing was evaluated by treating the beads in saline solution (0.9% w/v) at 30, 50, 63, and 72°C. The encapsulated probiotic bacteria were found alive even after treatment at 72°C for 90 s. Most of the free cells did not survive at the temperature higher than 50°C and very low pH (pH 2 and 3). The survival of probiotic cells was found higher with the hybrid hydrogel beads containing alginate and soy protein isolate (1:8 w/w). Furthermore, mango juice fortified with encapsulated L. plantarum in hydrogel beads was subjected to thermal pasteurization at 72°C for 90 s.

Staying alive: growth and survival of Bifidobacterium animalis subsp. animalis under in vitro and in vivo conditions

Members of the Bifidobacterium genus are widely used as probiotics in fermented milk products. Bifidobacterium animalis subsp. animalis CNCM I-4602 grows and survives poorly in reconstituted skimmed milk (RSM). Availing of genome and transcriptome information, this poor growth and survival phenotype in milk was substantially improved by the addition of certain compounds, such as yeast extract, uric acid, glutathione, cysteine, ferrous sulfate, and a combination of magnesium sulfate and manganese sulfate. Carbohydrate utilization of CNCM I-4602 was also investigated, allowing the identification of several carbohydrate utilization gene clusters, and highlighting this strain's inability to utilize lactose, unlike the type strain of this subspecies, B. animalis subsp. animalis ATCC25527 and the B. animalis subsp. lactis subspecies. In addition, the ability of B. animalis subsp. animalis CNCM I-4602 to colonize a murine model was investigated, which showed that this strain persists in the murine gut for a period of at least 4 weeks. Associated in vivo transcriptome analysis revealed that, among other genes, a gene cluster encoding a predicted type IVb tight adherence (Tad) pilus was upregulated, indicating that this extracellular structure plays a role in the colonization/adaptation of the murine gastrointestinal tract by this strain.

Investigating the transmissibility of tet(W) in bifidobacteria exposed to acid and bile stress

Transfer of antibiotic resistance genes from probiotic bacteria to pathogens poses a safety concern. Orally administered probiotics are exposed to stressful conditions during gastrointestinal transit. In this study, filter mating experiments were performed to investigate the potential role of exposure of Bifidobacterium isolates to acid and bile stress on the transfer of a tetracycline resistance gene, tet(W), to Enterococcus faecalis ATCC 51299. No E. faecalis transconjugants were obtained after mating with either stressed or unstressed Bifidobacterium, thereby suggesting that tet(W) could not be transferred as a result of exposure to gastrointestinal stresses.

P4P: a peptidome-based strain-level genome comparison web tool

Peptidome similarity analysis enables researchers to gain insights into differential peptide profiles, providing a robust tool to discriminate strain-specific peptides, true intra-species differences among biological replicates or even microorganism-phenotype variations. However, no in silico peptide fingerprinting software existed to facilitate such phylogeny inference. Hence, we developed the Peptidomes for Phylogenies (P4P) web tool, which enables the survey of similarities between microbial proteomes and simplifies the process of obtaining new biological insights into their phylogeny. P4P can be used to analyze different peptide datasets, i.e. bacteria, viruses, eukaryotic species or even metaproteomes. Also, it is able to work with whole proteome datasets and experimental mass-to-charge lists originated from mass spectrometers. The ultimate aim is to generate a valid and manageable list of peptides that have phylogenetic signal and are potentially sample-specific. Sample-to-sample comparison is based on a consensus peak set matrix, which can be further submitted to phylogenetic analysis. P4P holds great potential for improving phylogenetic analyses in challenging taxonomic groups, biomarker identification or epidemiologic studies. Notably, P4P can be of interest for applications handling large proteomic datasets, which it is able to reduce to small matrices while maintaining high phylogenetic resolution. The web server is available at http://sing-group.org/p4p.

Assessing the effects of exposure to environmental stress on some functional properties of Bifidobacterium animalis ssp. lactis

This study assessed the effects of exposing a strain of Bifidobacterium animalis ssp. lactis to acid, bile and osmotic stresses on antagonistic properties, biofilm formation and antibiotic susceptibility/resistance profile. Exposure to each stress factor appeared to have no significant effect on the antagonism against Escherichia coli NCTC 12900 and Salmonella enterica serovar Enteritidis PT4. No suppression in biofilm formation due to exposure to stress was observed. Bile and osmotic stresses resulted in significantly higher biofilm formation. Expression of an exopolysaccharide synthesis gene, gtf 01207, was significantly higher when the B. animalis ssp. lactis strain was exposed to osmotic stress. Susceptibility of the B. animalis ssp. lactis strain to chloramphenicol, erythromycin, ampicillin and vancomycin, and resistance to tetracycline remained unchanged when exposed to each stress. The expression of a tetracycline resistance gene, tet(W), was significantly higher when exposed to each stress. These results may suggest that the potential for the B. animalis ssp. lactis strain to provide probiotic benefit, after exposure to the stressful conditions of the gastrointestinal tract, remains intact.

Bifidobacterium bifidum as an example of a specialized human gut commensal

Bifidobacteria are considered dominant and for this reason key members of the human gut microbiota, particularly during the first one to two years following birth. A substantial proportion of the bifidobacterial population in the intestine of infants belong to the Bifidobacterium bifidum taxon, whose members have been shown to display remarkable physiological and genetic features involving adhesion to epithelia, as well as utilization of host-derived glycans. Here, we reviewed the current knowledge on the genetic features and associated adaptations of B. bifidum to the human gut.

Membrane fatty acid composition and fluidity are involved in the resistance to freezing of Lactobacillus buchneri R1102 and Bifidobacterium longum R0175

Determinations of membrane fatty acid composition and fluidity were used together with acidification activity and viability measurements to characterize the physiological state after freezing of Lactobacillus buchneri R1102 and Bifidobacterium longum R0175 cells harvested in the exponential and stationary growth phases. For both strains, lower membrane fluidity was achieved in cells harvested in the stationary growth phase. This change was linked to a lower unsaturated-to-saturated fatty acid ratio for both strains and a higher cyclic-to-saturated fatty acid ratio for L. buchneri R1102 alone. These membrane properties were linked to survival and to maintenance of acidification activity of the cells after freezing, which differed according to the strain and the growth phase. Survival of B. longum R0175 was increased by 10% in cells with low membrane fluidity and high relative saturated fatty acid contents, without any change in acidification activity. Acidification activity was more degraded (70 min) in L. buchneri R1102 cells displaying low membrane fluidity and high saturated and cyclic fatty acid levels. Finally, this study showed that membrane modifications induced by the growth phase differed among bacterial strains in terms of composition. By lowering membrane fluidity, these modifications could be beneficial for survival of B. longum R0175 during the freezing process but detrimental for maintenance of acidification activity of L. buchneri R1102.

Integrated transcriptomic and proteomic analysis of the bile stress response in a centenarian-originated probiotic Bifidobacterium longum BBMN68

Bifidobacteria are natural inhabitants of the human gastrointestinal tract and well known for their health-promoting effects. Tolerance to bile stress is crucial for bifidobacteria to survive in the colon and to exert their beneficial actions. In this work, RNA-Seq transcriptomic analysis complemented with proteomic analysis was used to investigate the cellular response to bile in Bifidobacterium longum BBMN68. The transcript levels of 236 genes were significantly changed (≥ threefold, p < 0.001) and 44 proteins were differentially abundant (≥1.6-fold, p < 0.01) in B. longum BBMN68 when exposed to 0.75 g l(-1) ox-bile. The hemolysin-like protein and bile efflux systems were significantly over produced, which might prevent bile adsorption and exclude bile, respectively. The cell membrane composition was modified probably by an increase of cyclopropane fatty acid and a decrease of transmembrane proteins, resulting in a cell membrane more impermeable to bile salts. Our hypothesis was later confirmed by surface hydrophobicity assay. The transcription of genes related to xylose utilization and bifid shunt were up-regulated, which increased the production of ATP and reducing equivalents to cope with bile-induced damages in a xylan-rich colon environment. Bile salts signal the B. longum BBMN68 to gut entrance and enhance the expression of esterase and sortase associated with adhesion and colonization in intestinal tract, which was supported by a fivefold increased adhesion ability to HT-29 cells by BBMN68 upon bile exposure. Notably, bacterial one-hybrid and EMSA assay revealed that the two-component system senX3-regX3 controlled the expression of pstS in bifidobacteria and the role of this target gene in bile resistance was further verified by heterologous expression in Lactococcus lactis. Taken altogether, this study established a model for global response mechanisms in B. longum to bile.

Immunomodulating activity of exopolysaccharide-producing Leuconostoc mesenteroides strain NTM048 from green peas

AIMS

The present work was aimed to find novel probiotics to enhance the mucosal barrier function of humans. The effectiveness was evaluated in vitro and in vivo.

METHODS AND RESULTS

Stimulation of IgA production in mucosal surfaces is one of the most beneficial traits of lactic acid bacteria (LAB) for enhancing the barrier. Therefore, 173 LAB strains were evaluated for the ability to induce IgA production using murine Peyer's patch cells. Strain NTM048 isolated from green peas showed the highest activity and was identified as Leuconostoc mesenteroides subsp. mesenteroides. This strain was found to tolerate gastrointestinal digestion and produce large amounts of exopolysaccharides, which possess IgA-inducing activity. Dietary supplementation with NTM048 induced a significant increase in the faecal IgA content and plasma IgA levels of BALB/cA mice. A gene expression analysis of Peyer's patch cells revealed that the transforming growth factor-β and activation-induced cytidine deaminase genes were upregulated by NTM048 intake.

CONCLUSIONS

Strain NTM048 stimulates Peyer's patch cells to induce intestinal and systemic immune response, revealing the potential of NTM048 as a probiotic for enhancing the mucosal barrier function.

SIGNIFICANCE AND IMPACT OF THE STUDY

This report demonstrates a food-applicable Leuconostoc mesenteroides strain secreting exopolysaccharide that shows high IgA-inducing ability.

Isolation, identification and characterisation of three novel probiotic strains (Lactobacillus paracasei CNCM I-4034, Bifidobacterium breve CNCM I-4035 and Lactobacillus rhamnosus CNCM I-4036) from the faeces of exclusively breast-fed infants

The aim of the present study was to isolate, identify and characterise novel strains of lactic acid bacteria and bifidobacteria with probiotic properties from the faeces of exclusively breast-fed infants. Of the 4680 isolated colonies, 758 exhibited resistance to low pH and tolerance to high concentrations of bile salts; of these, only forty-two exhibited a strong ability to adhere to enterocytes in vitro. The identities of the isolates were confirmed by 16S ribosomal RNA (rRNA) sequencing, which permitted the grouping of the forty-two bacteria into three different strains that showed more than 99 % sequence identity with Lactobacillus paracasei, Lactobacillus rhamnosus and Bifidobacterium breve, respectively. The strain identification was confirmed by sequencing the 16S-23S rRNA intergenic spacer regions. Strains were assayed for enzymatic activity and carbohydrate utilisation, and they were deposited in the Collection Nationale de Cultures de Microorganismes (CNCM) of the Institute Pasteur and named L. paracasei CNCM I-4034, B. breve CNCM I-4035 and L. rhamnosus CNCM I-4036. The strains were susceptible to antibiotics and did not produce undesirable metabolites, and their safety was assessed by acute ingestion in immunocompetent and immunosuppressed BALB/c mouse models. The three novel strains inhibited in vitro the meningitis aetiological agent Listeria monocytogenes and human rotavirus infections. B. breve CNCM I-4035 led to a higher IgA concentration in faeces and plasma of mice. Overall, these results suggest that L. paracasei CNCM I-4034, B. breve CNCM I-4035 and L. rhamnosus CNCM I-4036 should be considered as probiotic strains, and their human health benefits should be further evaluated.

Selection of a Bifidobacterium animalis subsp. lactis strain with a decreased ability to produce acetic acid

We have characterized a new strain, Bifidobacterium animalis subsp. lactis CECT 7953, obtained by random UV mutagenesis, which produces less acetic acid than the wild type (CECT 7954) in three different experimental settings: De Man-Rogosa-Sharpe broth without sodium acetate, resting cells, and skim milk. Genome sequencing revealed a single Phe-Ser substitution in the acetate kinase gene product that seems to be responsible for the strain's reduced acid production. Accordingly, acetate kinase specific activity was lower in the low acetate producer. Strain CECT 7953 produced less acetate, less ethanol, and more yoghourt-related volatile compounds in skim milk than the wild type did. Thus, CECT 7953 shows promising potential for the development of dairy products fermented exclusively by a bifidobacterial strain.

Short communication: the complete genome sequence of Bifidobacterium animalis subspecies animalis ATCC 25527(T) and comparative analysis of growth in milk with B. animalis subspecies lactis DSM 10140(T)

The objective of this work was to sequence the genome of Bifidobacterium animalis ssp. animalis ATCC 25527(T), the subspecies most closely related to B. animalis ssp. lactis, some strains of which are widely added to dairy foods as probiotics. The complete 1,932,963-bp genome was determined by a combination of 454-shotgun sequencing and PCR gap closing, and the completed assembly was verified by comparison with a KpnI optical map. Comparative analysis of the B. animalis ssp. animalis ATCC 25527(T) and B. animalis ssp. lactis DSM 10140(T) genomes revealed high degrees of synteny and sequence homology. Comparative genomic analysis revealed 156 and 182 genes that were unique to and absent in the B. animalis ssp. animalis genome, respectively. Among these was a set of unique clustered regularly interspaced short palindromic repeats (CRISPR)-associated genes and a novel CRISPR locus containing 30 spacers in the genome of B. animalis ssp. animalis. Although previous researchers have suggested that one of the defining phenotypic differences between B. animalis ssp. animalis and B. animalis ssp. lactis is the ability of the latter to grow in milk and milk-based media, the differential gene content did not provide insights to explain these differences. Furthermore, growth and acid production in milk and milk-based media did not differ significantly between B. animalis ssp. lactis (DSM 10140(T) and Bl04) and B. animalis ssp. animalis (ATCC 25527(T)). Growth of these strains in supplemented milk suggested that growth was limited by a lack of available low-molecular-weight nitrogen in the 3 strains examined.

Acquired tolerance to oxidative stress in Bifidobacterium longum 105-A via expression of a catalase gene

For improvement of tolerance to oxidative stress in Bifidobacterium longum 105-A, we introduced the Bacillus subtilis catalase gene (katE) into it. The transformant showed catalase activity (39 U/mg crude protein) in the intracellular fraction, which increased survival by ∼100-fold after a 1-h exposure to 4.4 mM H(2)O(2), decreased de novo H(2)O(2) accumulation, and increased survival in aerated cultures by 10(5)-fold at 24 h. The protection level was better than that conferred by exogenously added catalase.