Harnessing the endogenous Type I-C CRISPR-Cas system for genome editing in Bifidobacterium breve.

Bifidobacterium breve, one of the main bifidobacterial species colonizing the human gastrointestinal tract in early life, has received extensive attention for its purported beneficial effects on human health. However, exploration of the mode of action of such beneficial effects exerted by B. breve is cumbersome due to the lack of effective genetic tools, which limits its synthetic biology application. The widespread presence of CRISPR-Cas systems in the B. breve genome makes endogenous CRISPR-based gene editing toolkits a promising tool. This study revealed that Type I-C CRISPR-Cas systems in B. breve can be divided into two groups based on the amino acid sequences encoded by cas gene clusters. Deletion of the gene coding uracil phosphoribosyl-transferase (upp) was achieved in five B. breve strains from both groups using this system. In addition, translational termination of uracil phosphoribosyl-transferase was successfully achieved in B. breve FJSWX38M7 by single-base substitution of the upp gene and insertion of three stop codons. The gene encoding linoleic acid isomerase (bbi) in B. breve, being a characteristic trait, was deleted after plasmid curing, which rendered it unable to convert linoleic acid into conjugated linoleic acid, demonstrating the feasibility of successive editing. This study expands the toolkit for gene manipulation in B. breve and provides a new approach toward functional genome editing and analysis of B. breve strains.IMPORTANCEThe lack of effective genetic tools for Bifidobacterium breve is an obstacle to studying the molecular mechanisms of its health-promoting effects, hindering the development of next-generation probiotics. Here, we introduce a gene editing method based on the endogenous CRISPR-Cas system, which can achieve gene deletion, single-base substitution, gene insertion, and successive gene editing in B. breve. This study will facilitate discovery of functional genes and elucidation of molecular mechanisms of B. breve pertaining to health-associated benefits.

The therapeutic potential of dietary intervention: based on the mechanism of a tryptophan derivative-indole propionic acid on metabolic disorders.

Tryptophan (TRP) contributes to individual immune homeostasis and good condition via three complex metabolism pathways (5-hydroxytryptamine (5-HT), kynurenine (KP), and gut microbiota pathway). Indole propionic acid (IPA), one of the TRP derivatives of the microbiota pathway, has raised more attention because of its impact on metabolic disorders. Here, we retrospect increasing evidence that TRP metabolites/IPA derived from its proteolysis impact host health and disease. IPA can activate the immune system through aryl hydrocarbon receptor (AHR) and/or Pregnane X receptor (PXR) as a vital mediator among diet-caused host and microbe cross-talk. Different levels of IPA in systemic circulation can predict the risk of NAFLD, T2DM, and CVD. IPA is suggested to alleviate cognitive impairment from oxidative damage, reduce gut inflammation, inhibit lipid accumulation and attenuate the symptoms of NAFLD, putatively enhance the intestinal epithelial barrier, and maintain intestinal homeostasis. Now, we provide a general description of the relationships between IPA and various physiological and pathological processes, which support an opportunity for diet intervention for metabolic diseases.

Interaction of beta-glucans with gut microbiota: Dietary origins, structures, degradation, metabolism, and beneficial function.

Beta-glucan (BG), a polysaccharide comprised of interfacing glucose monomers joined via beta-glycosidic linkages, can be defined as a type of dietary fiber with high specificity based on its interaction with the gut microbiota. It can induce similar interindividual microbiota responses, thereby having beneficial effects on the human body. In this paper, we review the four main sources of BG (cereals, fungi, algae, and bacteria) and their differences in structure and content. The interaction of BG with gut microbiota and the resulting health effects have been highlighted, including immune enhancement, regulation of serum cholesterol and insulin levels, alleviation of obesity and improvement of cognitive disorders. Finally, the application of BG in food products and its beneficial effects on the gut microbiota of consumers were discussed. Although some of the mechanisms of action remain unclear, revealing the beneficial functions of BG from the perspective of gut microbiota can help provide theoretical support for the development of diets that target the regulation of microbiota.

Gut microbiota and anti-aging: Focusing on spermidine.

The human gut microbiota plays numerous roles in regulating host growth, the immune system, and metabolism. Age-related changes in the gut environment lead to chronic inflammation, metabolic dysfunction, and illness, which in turn affect aging and increase the risk of neurodegenerative disorders. Local immunity is also affected by changes in the gut environment. Polyamines are crucial for cell development, proliferation, and tissue regeneration. They regulate enzyme activity, bind to and stabilize DNA and RNA, have antioxidative properties, and are necessary for the control of translation. All living organisms contain the natural polyamine spermidine, which has anti-inflammatory and antioxidant properties. It can regulate protein expression, prolong life, and improve mitochondrial metabolic activity and respiration. Spermidine levels experience an age-related decrease, and the development of age-related diseases is correlated with decreased endogenous spermidine concentrations. As more than just a consequence, this review explores the connection between polyamine metabolism and aging and identifies advantageous bacteria for anti-aging and metabolites they produce. Further research is being conducted on probiotics and prebiotics that support the uptake and ingestion of spermidine from food extracts or stimulate the production of polyamines by gut microbiota. This provides a successful strategy to increase spermidine levels.

Anti-Inflammatory, Barrier Maintenance, and Gut Microbiome Modulation Effects of Saccharomyces cerevisiae QHNLD8L1 on DSS-Induced Ulcerative Colitis in Mice.

The use of probiotics has been considered as a new therapy option for ulcerative colitis (UC), and yeast has recently received widespread recommendation for human health. In this study, the probiotic characteristics of four yeast strains, Saccharomyces boulardii CNCMI-745, Kluyveromyces marxianus QHBYC4L2, Saccharomyces cerevisiae QHNLD8L1, and Debaryomyces hansenii QSCLS6L3, were evaluated in vitro; their ability to ameliorate dextran sulfate sodium (DSS)-induced colitis was investigated. Among these, S. cerevisiae QHNLD8L1 protected against colitis, which was reflected by increased body weight, colon length, histological injury relief, decreased gut inflammation markers, and intestinal barrier restoration. The abundance of the pathogenic bacteria Escherichia-Shigella and Enterococcaceae in mice with colitis decreased after S. cerevisiae QHNLD8L1 treatment. Moreover, S. cerevisiae QHNLD8L1 enriched beneficial bacteria Lactobacillus, Faecalibaculum, and Butyricimonas, enhanced carbon metabolism and fatty acid biosynthesis function, and increased short chain fatty acid (SCFAs) production. Taken together, our results indicate the great potential of S. cerevisiae QHNLD8L1 supplementation for the prevention and alleviation of UC.

Antibiotic-induced gut dysbiosis and barrier disruption and the potential protective strategies.

The oral antibiotic therapies administered widely to people and animals can cause gut dysbiosis and barrier disruption inevitably. Increasing attention has been directed toward antibiotic-induced gut dysbiosis, which involves a loss of diversity, changes in the abundances of certain taxa and consequent effects on their metabolic capacity, and the spread of antibiotic-resistant bacterial strains. Treatment with beta-lactam, glycopeptide, and macrolide antibiotics is associated with the depletion of beneficial commensal bacteria in the genera Bifidobacterium and Lactobacillus. The gut microbiota is a reservoir for antibiotic resistance genes, the prevalence of which increases sharply after antibiotic ingestion. The intestinal barrier, which comprises secretory, physical, and immunological barriers, is also a target of antibiotics. Antibiotic induced changes in the gut microbiota composition could induce weakening of the gut barrier through changes in mucin, cytokine, and antimicrobial peptide production by intestinal epithelial cells. Reports have indicated that dietary interventions involving prebiotics, probiotics, omega-3 fatty acids, and butyrate supplementation, as well as fecal microbiota transplantation, can alleviate antibiotic-induced gut dysbiosis and barrier injuries. This review summarizes the characteristics of antibiotic-associated gut dysbiosis and barrier disruption, as well as the strategies for alleviating this condition. This information is intended to provide a foundation for the exploration of safer, more efficient, and affordable strategies to prevent or relieve antibiotic-induced gut injuries.

Anti-aging effects and mechanisms of anthocyanins and their intestinal microflora metabolites.

Aging, a natural and inevitable physiological process, is the primary risk factor for all age-related diseases; it severely threatens the health of individuals and places a heavy burden on the public health-care system. Thus, strategies to extend the lifespan and prevent and treat age-related diseases have been gaining increasing scientific interest. Anthocyanins (ACNs) are a subclass of flavonoids widely distributed in fruits and vegetables. Growing evidence suggests that ACNs delay aging and relieve age-related diseases. However, owing to the low bioavailability of ACNs, their gut metabolites have been proposed to play a critical role in mediating health benefits. In this review, we introduce the biological fate of ACNs after consumption and highlight ACNs metabolites (phenolic acids) from intestinal microorganisms. Additionally, ACNs and gut metabolites exhibit outstanding anti-aging ability in Caenorhabditis elegans, Drosophila melanogaster, and mouse models, probably associated with increasing antioxidation, anti-inflammation, protein homeostasis, antiglycation, mitochondrial function, and inhibition of insulin/IGF-1 signaling (IIS). ACNs and gut metabolites have great application prospects as functional foods and drugs to delay aging and manage age-related diseases. Further investigation should focus on the interaction between ACNs and gut microbiota, including clarifying the complex metabolic pathway and maximizing the health effects of ACNs.

Latilactobacillus sakei: a candidate probiotic with a key role in food fermentations and health promotion.

Latilactobacillus sakei is used extensively in industrial production and food fermentations. The species is primarily derived from fermented meat and vegetable products and is also found in human feces. Genomics and metabolomics have revealed unique metabolic pathways in L. sakei and molecular mechanisms underlying its competitive advantages in different habitats, which are mostly attributed to its flexible carbohydrate metabolism, cold tolerance, acid and salt tolerance, ability to cope with oxygen changes, and heme uptake. In recent years, probiotic effects of L. sakei and its metabolites have been identified, including the ability to effectively alleviate metabolic syndrome, inflammatory bowel disease, and atopic dermatitis. This review summarizes the genomic and metabolic characteristics of L. sakei and its metabolites and describes their applications, laying a foundation for their expanded use across the food and healthcare industries.

Novel Phocaeicola Strain Ameliorates Dextran Sulfate Sodium-induced Colitis in Mice.

Previously, we isolated a novel Phocaeicola strain, Phocaeicola faecalis FXJYN30E22, from the feces of a healthy human from China. Metagenomic analysis revealed that the distribution of FXJYN30E22 differed in the intestinal tract of different hosts. We aimed to determine whether FXJYN30E22 protects against ulcerative colitis by employing a mouse model. In this study, dextran sulfate sodium was used to construct the UC model. The disease activity index, colon length, body weight changes, and histological scores were used as the pathological indicators to assess the anti-inflammatory effect of P. faecalis FXJYN30E22. Further, cytokine levels, tight junction mRNA expression levels, and short-chain fatty acid (SCFA) concentrations were also analyzed. Phocaeicola faecalis FXJYN30E22 could reduce the DSS-induced increase in DAI score, and enhance the colon length and body weight. Phocaeicola faecalis FXJYN30E22 could enhance TJ protein concentration and modulate the level of cytokines to reach levels close to those of the control group. FXJYN30E22 could also upregulate the concentrations of SCFA, which include acetate and butyrate. Based on the correlation analysis, four factors, including interleukin (IL)-6, IL-10, IL-1ß levels, and propionate concentration, were related to the protective roles of FXJYN30E22 in UC mice to different degrees. According to an analysis of the genomic information, the potential protective effects of strain FXJYN30E22 may be associated with the secretion of SCFA by specific genes. These findings suggest that oral P. faecalis FXJYN30E22 could help maintain the epithelial barrier by regulating cytokine levels and secreting SCFA.

Insights into the Metabolic Response of Lactiplantibacillus plantarum CCFM1287 upon Patulin Exposure.

Patulin (PAT) is a common mycotoxin in the food industry, and is found in apple products in particular. Consumption of food or feed contaminated with PAT can cause acute or chronic toxicity in humans and animals. Lactiplantibacillus plantarum CCFM1287 is a probiotic strain that effectively degrades PAT in PBS and food systems. In this study, it was found that the concentration of PAT (50 mg/L) in MRS medium decreased by 85.09% during the first stages of CCFM1287 growth, and this change was consistent with the first-order degradation kinetic model. Meanwhile, the regulation of oxidative stress by L. plantarum CCFM1287 in response to PAT exposure and metabolic changes that occur during PAT degradation were investigated. The degree of intracellular damage was attenuated after 16 h of exposure compared to 8 h. Meanwhile, metabolomic data showed that 30 and 29 significantly different metabolites were screened intracellularly in the strain after 8 h and 16 h of PAT stress at 50 mg/L, respectively. The results of pathway enrichment analysis suggested that the purine metabolic pathway was significantly enriched at both 8 h and 16 h. However, as is consistent with the performance of the antioxidant system, the changes in Lactiplantibacillus diminished with increasing time of PAT exposure. Therefore, this study helps to further explain the mechanism of PAT degradation by L. plantarum CCFM1287.

Characteristics of an In Vitro Mesenteric Lymph Node Cell Suspension Model and Its Possible Association with In Vivo Functional Evaluation.

In a previous study, we uncovered three immune-responsive patterns of gut microbes using an in vitro mesenteric lymph node cell suspension model, abbreviated as the MLN model hereafter. We used Akkermansia muciniphila and Clostridium butyricum as the first group directly inducing an immune response, Bifidobacterium sp. and Bacteroides sp. as the second group evoking an immune response with the help of stimuli (anti-CD3 and anti-CD28 antibodies), and Lactobacillus sp. as the third group blunting the immune response with or without stimuli. Our group previously clarified the immune-activation characteristics of A. muciniphila and linked its in vivo immune induction effect in GF and SPF mice under homeostasis. In the present study, we supplemented the characteristics of C. butyricum and B. bifidum in the in vitro MLN model and addressed the specific elements of the model. Finally, we used an in vivo TNBS-challenge model to show the functional differences between these species with different response patterns in vitro. The results showed that C. butyricum and B. bifidum evoked an immune response in vitro in a dose-dependent and strain-unique manner. Although TLR2, rather than TLR4, is indispensable for immune activation in the present in vitro model, it may not involve interaction between TLR2 and bacterial ligands. Like the PBMC model, the present in vitro MLN model is highly dependent on cell resources and should be given more attention when used to conduct a quantitative comparison. Finally, a mixture of two strong immunogenic strains, A. muciniphila and C. butyricum, significantly increased the mortality of TNBS-challenged (2,4,6-trinitrobenzene sulfonic acid, TNBS) mice, indicating a possible link between the in vitro MLN model and in vivo functional evaluation. However, more evidence is needed to clarify the associations and underlying mechanisms.

Evaluation of the Potential Protective Effects of Lactobacillus Strains against Helicobacter pylori Infection: A Randomized, Double-Blinded, Placebo-Controlled Trial.

Background: The beneficial effects of probiotic supplementation standard antibiotic therapies for Helicobacter pylori infection have been verified, but the ability of probiotic monotherapy to eradicate H. pylori remains unclear. Aim: To evaluate the accuracy and efficacy of specific Lactobacillus strains against H. pylori infection. Methods: Seventy-eight patients with H. pylori infection were treated with strain L. crispatus G14-5M (L. crispatus CCFM1118) or L. helveticus M2-09-R02-S146 (L. helveticus CCFM1121) or L. plantarum CCFM8610 at a dose of 2 g twice daily for one month. 14C-urea breath test, the gastrointestinal symptom rating scale, serum pepsinogen concentrations, and serum cytokine concentrations of patients were measured at baseline and end-of-trial to analyze the effect of the Lactobacillus strains in eradicating H. pylori infection and reducing gastrointestinal discomfort in patients. In addition, the composition and abundance of the intestinal microbiota of patients were also measured at end-of-trial. Results: The 14C-urea breath test value of the three Lactobacillus treatment groups had decreased significantly, and the eradication rate of H. pylori had increased by the end of the trial. In particular, the eradication rate in the G14-5M treatment group was significantly higher than the placebo group (70.59% vs. 15.38%, P=0.0039), indicating that one-month administration of the G14-5M regimen was sufficient to eradicate H. pylori infection. The ingestion of Lactobacillus strains also ameliorated the gastrointestinal symptom rating scale scores, and the serum interleukin-8 concentrations of H. pylori-infected patients appeared to modulate the gut microbiota of patients. However, none of the Lactobacillus strains had a significant effect on general blood physiological characteristics, serum tumor necrosis factor α concentrations, or serum pepsinogen concentrations in the patients. Conclusion: Three Lactobacillus strains significantly alleviate the gastrointestinal discomfort and the gastric inflammatory response of H. pylori-infected patients. The activity of probiotics in eradicating H. pyloriinfection may be species/strain specific.

Phocaeicola faecalis sp. nov., a strictly anaerobic bacterial strain adapted to the human gut ecosystem.

A novel strictly anaerobic, Gram-negative bacterium, designated as strain FXJYN30E22T, was isolated from the feces of a healthy woman in Yining county, Xinjiang province, China. This strain was non-spore-forming, bile-resistant, non-motile and rod-shaped. It was found to belong to a single separate group in the Phocaeicola genus based on its 16 S ribosomal RNA (rRNA) gene sequence. Alignments of 16 S rRNA gene sequences showed only a low sequence identity (≤ 95.5 %) between strain FXJYN30E22T and all other Phocaeicola strains in public data bases. The genome (43.0% GC) of strain FXJYN30E22T was sequenced, and used for phylogenetic analysis which showed that strain FXJYN30E22T was most closely related to the type strain Phocaeicola massiliensis JCM 13223T. The average nucleotide identity (ANI) value and digital DNA-DNA hybridization (dDDH) between FXJYN30E22T and P. massiliensis JCM 13223T were 90.4 and 41.9 %, which were lower than the generally accepted species boundaries (94.0 and 70 %, respectively). The major cellular fatty acids and polar lipids were anteiso-branched C15:0 and phosphatidylethanolamine, respectively. The result of genome annotation and KEGG analysis showed that strain FXJYN30E22T contains a number of genes in polysaccharide and fatty acid synthesis that indicated adaptation to the human gut system. Furthermore, a pbpE (penicillin-binding protein) gene was found in the genome of strain FXJYN30E22T but in no other Phocaeicola species, which suggested this gene might be contribute to the adaptive capacity of strain FXJYN30E22T. Based on our data, strain FXJYN30E22T (= CGMCC1.17870T/KCTC25195T) was classified as a novel Phocaeicola species, and the name Phocaeicola faecalis sp. nov., was proposed.

Evaluation of indigenous lactic acid bacteria of raw mare milk from pastoral areas in Xinjiang, China, for potential use in probiotic fermented dairy products.

In the present study 114 lactic acid bacteria strains, isolated from raw mare milks from pastoral areas for ethnic minorities in northwest China, were screened for probiotic traits, and their characteristics were compared with those of Lactobacillus rhamnosus GG, a commercial strain. Among the 114 strains identified, the most common species was Pediococcus pentosaceus (n = 52), followed by Leuconostoc lactis (n = 35), Lactobacillus helveticus (n = 7), Lactobacillus plantarum (n = 6), Lactobacillus kefiri (n = 5), Lactobacillus curvatus (n = 4), Lactobacillus paracasei (n = 3), and Lactococcus garvieae (n = 3). Based on acid and bile salt tolerance, 15 strains were further selected. All selected strains were subjected to a series of in vitro tests to assess their technological properties, including cell surface hydrophobicity (13.6-56.2%), autoaggregation ability (9.26-38.30%), coaggregation ability, and heat and lysozyme survival rates (84.74-94.01% and 80.52-99.37%, respectively). In vitro antagonism showed that Lb. plantarum (M5-19, M8-60, M8-59) exhibited the most strong inhibitory activity against 7 tested pathogens. Moreover, antibiotic resistance and hemolytic activity were investigated for safety assessment. No strain exhibited hemolytic activity, and most of the strains were sensitive to a series of 14 antibiotics of clinical importance. Ultimately, the principal component analysis of all data obtained above showed that 2 Lb. plantarum strains (M8-59, M8-60) and Lb. paracasei M1-36 exhibited the best potential for their inclusion as adjunct functional cultures in local fermented dairy products.

Protective Effects of Lactobacillus plantarum CCFM8610 against Acute Toxicity Caused by Different Food-Derived Forms of Cadmium in Mice.

Cadmium (Cd) is an environmental pollutant that is toxic to almost every human organ. Oral supplementation with lactic acid bacteria (LAB) has been reported to alleviate cadmium toxicity. However, research on the mitigation of cadmium toxicity by LAB is still limited to inorganic cadmium, which is not representative of the varied forms of cadmium ingested daily. In this study, different foodborne forms of cadmium were adopted to establish an in vivo toxicity model, including cadmium-glutathione, cadmium-citrate, and cadmium-metallothionein. The ability of Lactobacillus plantarum CCFM8610 to reduce the toxic effects of these forms of cadmium was further investigated. The 16S rRNA gene sequencing and metabolomics technologies based on liquid chromatography with tandem mass spectrometry (LC-MS/MS) were adopted for the exploration of relevant protective mechanisms. The results demonstrated that the consumption of CCFM8610 can reduce the content of cadmium in mice and relieve the oxidative stress caused by different food-derived forms of cadmium, indicating that CCFM8610 has a promising effect on the remediation of the toxic effects of cadmium food poisoning. Meanwhile, protective effects on gut microflora and serum metabolites might be an important mechanism for probiotics to alleviate cadmium toxicity. This study provides a theoretical basis for the application of L. plantarum CCFM8610 to alleviate human cadmium poisoning.

Genotyping and plant-derived glycan utilization analysis of Bifidobacterium strains from mother-infant pairs.

BACKGROUND: Bifidobacteria are important probiotics; some of the beneficial effects of bifidobacteria are achieved by the hydrolysis of glycans in the human gut. However, because the diet of breastfed infants typically lacks plant-derived glycans, in the gut environment of mothers and their breastfed infants, the mother will intake a variety of plant-derived glycans, such as from onions and bananas, through her diet. Under this assumption, we are interested in whether the same species of bifidobacteria isolated from mother-infant pairs present a distinction in their hydrolysis of plant-derived carbohydrates. RESULTS: Among the 36 Bifidobacterium strains, bifidobacterial carbohydrate utilization showed two trends related to the intestinal environment where the bacteria lived. Compared with infant-type bifidobacterial strains, adult-type bifidobacterial strains preferred to use plant-derived glycans. Of these strains, 10 isolates, 2 Bifidobacterium pseudocatenulatum (B. pseudocatenulatum), 2 Bifidobacterium pseudolongum (B. pseudolongum), 2 Bifidobacterium bifidum (B. bifidum), 2 Bifidobacterium breve (B. breve), and 2 Bifidobacterium longum (B. longum), were shared between the mother-infant pairs. Moreover, the repetitive sequence-based polymerase chain reaction (rep-PCR) results illustrated that B. pseudolongum and B. bifidum showed genotypic similarities of 95.3 and 98.2%, respectively. Combined with the carbohydrate fermentation study, these results indicated that the adult-type strains have a stronger ability to use plant-derived glycans than infant-type strains. Our work suggests that bifidobacterial carbohydrate metabolism differences resulted in the selective adaptation to the distinct intestinal environment of an adult or breastfed infant. CONCLUSIONS: The present study revealed that the different gut environments can lead to the differences in the polysaccharide utilization in the same strains of bifidobacterial strains, suggesting a further goal of investigating the exact expression of certain enzymes in response to specific carbon sources.

Surface components and metabolites of probiotics for regulation of intestinal epithelial barrier.

The gut microbiota can significantly affect the function of the intestinal barrier. Some intestinal probiotics (such as Lactobacillus, Bifidobacteria, a few Escherichia coli strains, and a new generation of probiotics including Bacteroides thetaiotaomicron and Akkermansia muciniphila) can maintain intestinal epithelial homeostasis and promote health. This review first summarizes probiotics' regulation of the intestinal epithelium via their surface compounds. Surface layer proteins, flagella, pili and capsular polysaccharides constitute microbial-associated molecular patterns and specifically bind to pattern recognition receptors, which can regulate signaling pathways to produce cytokines or inhibit apoptosis, thereby attenuating inflammation and enhancing the function of the gut epithelium. The review also explains the effects of metabolites (such as secreted proteins, organic acids, indole, extracellular vesicles and bacteriocins) of probiotics on host receptors and the mechanisms by which these metabolites regulate gut epithelial barrier function. Previous reviews summarized the role of the surface macromolecules or metabolites of gut microbes (including both probiotics and pathogens) in human health. However, these reviews were mostly focused on the interactions between these substances and the intestinal mucosal immune system. In the current review, we only focused on probiotics and discussed the molecular interaction between these bacteria and the gut epithelial barrier.

Antimicrobial activities and in vitro properties of cold-adapted Lactobacillus strains isolated from the intestinal tract of cold water fishes of high latitude water areas in Xinjiang, China.

BACKGROUND: There are still a large variety of microorganisms among aquatic animals, especially probiotic lactic acid bacteria in cold water fishes at high latitudes have not been fully developed. Hence, the present study aims to evaluate the probiotic potential of cold-adapted Lactobacillus strains isolated from the intestinal tract of cold water fishes (Xinjiang) and select candidates to be used as new food preservative agents and/or probiotic additives in feeding of aquaculture. RESULTS: A total of 43 Lactobacillus spp. were isolated from 16 kinds of intestinal tract of cold-water fishes. They were characterized by phenotypic methods, identified using Rep-PCR and 16S rRNA gene sequencing as four species: Lactobacillus sakei (22 isolates), Lactobacillus plantarum (16 isolates), Lactobacillus casei (4 isolates) and Lactobacillus paracasei (1 isolate). The in vitro tests included survival in low pH and bile, antimicrobial activity (against Escherichia coli, Salmonella enterica subsp. enterica serovar Typhimurium, Salmonella enterica subsp. enterica, Listeria monocytogenes, and Listeria innocua), resistance to 15 antibiotics and hemolytic tests. Among all 43 lactobacilli isolates, the 22 isolates showed a wide range of antimicrobial activity against 6 different pathogenic strains. There were twenty isolates growing at optimal temperature ranging 16~20 °C, which were initially considered to be cold-adapted strains. Two (2) Lb. sakei strains and 2 Lb. plantarum strains demonstrated the highest survivability after 4 h of exposure at pH 2.0. Most of the tested strains cannot be cultured after exposed into 0.5% bile solution for 4 h, while 2 Lb. plantarum strains (E-HLM-3, CQ-CGC-2) and 1 Lb. sakei strain M-DGM-2 survived even at 2% bile concentration. In addition, the safety assessment showed that 22 strains without any detectable hemolytic activity and resistant to glycopeptides (vancomycin, teicoplanin), levofloxacin, aztreonam, amikacin and oxacillin, while all the studied lactobacilli showed sensitivity to or semi-tolerant to other antibiotics. CONCLUSIONS: Based on all the experiments, 3 strains, including E-HLM-3, CQ-CGC-2, and M-DGM-2 might be a candidate of choice for using in the food preservative agents and/or probiotic additives in feeding of aquaculture.

Oligosaccharides as co-encapsulating agents: effect on oral Lactobacillus fermentum survival in a simulated gastrointestinal tract.

OBJECTIVES: Four kinds of oligosaccharides were used as co-encapsulating agents to test the effect of extrusion-based microencapsulation on protection of Lactobacillus fermentum L7 against exposure to simulated gastric and intestinal juices as well as long-term refrigeration storage at 4 °C. RESULTS: The combination of alginate with galacto-oligosaccharides, isomalto-oligosaccharides, fructo-oligosaccharides, and xylo-oligosaccharides, or alginate alone exhibited good properties of the beads. The diameters of the cell beads co-encapsulated with oligosaccharides and encapsulated with alginate alone were similar, in the range of 2.34-2.51 mm. However, the encapsulation yield of L. fermentum cells co-encapsulated with oligosaccharides, which was in the range of 79.52-89.75%, was significantly higher than that of cells encapsulated with alginate alone. The capsules were stable in gastric conditions and can disintegrated when exposed to intestinal conditions. Additionally, the viability of microencapsulated cells after exposure to the simulated gastric and intestinal juices as well as long-term refrigeration storage was better than that of free cells, and the viability of cells co-encapsulated with oligosaccharides was better than that of cells encapsulated with alginate alone. Furthermore, fructo-oligosaccharides used as co-encapsulating agent showed the best performance. CONCLUSIONS: Microencapsulating L. fermentum with oligosaccharides protected cells well at a low temperature and offered effective gastrointestinal delivery of probiotics, and thus has the potential to maintain bacterial survival in probiotic products and will provide the research basis for design of effective probiotic-prebiotic combinations to maximize host benefit.

Lactic Acid Bacteria as Antifungal and Anti-Mycotoxigenic Agents: A Comprehensive Review.

Fungal contamination of food and animal feed, especially by mycotoxigenic fungi, is not only a global food quality concern for food manufacturers, but it also poses serious health concerns because of the production of a variety of mycotoxins, some of which present considerable food safety challenges. In today's mega-scale food and feed productions, which involve a number of processing steps and the use of a variety of ingredients, fungal contamination is regarded as unavoidable, even good manufacturing practices are followed. Chemical preservatives, to some extent, are successful in retarding microbial growth and achieving considerably longer shelf-life. However, the increasing demand for clean label products requires manufacturers to find natural alternatives to replace chemically derived ingredients to guarantee the clean label. Lactic acid bacteria (LAB), with the status generally recognized as safe (GRAS), are apprehended as an apt choice to be used as natural preservatives in food and animal feed to control fungal growth and subsequent mycotoxin production. LAB species produce a vast spectrum of antifungal metabolites to inhibit fungal growth; and also have the capacity to adsorb, degrade, or detoxify fungal mycotoxins including ochratoxins, aflatoxins, and Fusarium toxins. The potential of many LAB species to circumvent spoilage associated with fungi has been exploited in a variety of human food and animal feed stuff. This review provides the most recent updates on the ability of LAB to serve as antifungal and anti-mycotoxigenic agents. In addition, some recent trends of the use of LAB as biopreservative agents against fungal growth and mycotoxin production are highlighted.