Screening of Probiotic Activities of Lactobacilli Strains Isolated from Traditional Tibetan Qula, A Raw Yak Milk Cheese

Milk and Its Derivatives as Sources of Components and Microorganisms with Health-Promoting Properties: Probiotics and Bioactive Peptides

Milk is a source of many valuable nutrients, including minerals, vitamins and proteins, with an important role in adult health. Milk and dairy products naturally containing or with added probiotics have healthy functional food properties. Indeed, probiotic microorganisms, which beneficially affect the host by improving the intestinal microbial balance, are recognized to affect the immune response and other important biological functions. In addition to macronutrients and micronutrients, biologically active peptides (BPAs) have been identified within the amino acid sequences of native milk proteins; hydrolytic reactions, such as those catalyzed by digestive enzymes, result in their release. BPAs directly influence numerous biological pathways evoking behavioral, gastrointestinal, hormonal, immunological, neurological, and nutritional responses. The addition of BPAs to food products or application in drug development could improve consumer health and provide therapeutic strategies for the treatment or prevention of diseases. Herein, we review the scientific literature on probiotics, BPAs in milk and dairy products, with special attention to milk from minor species (buffalo, sheep, camel, yak, donkey, etc.); safety assessment will be also taken into consideration. Finally, recent advances in foodomics to unveil the probiotic role in human health and discover novel active peptide sequences will also be provided.

Alpha-amylase and alphaglucosidase inhibitory properties, beta-galactosidase activity, and probiotic potential of lactic acid bacteria and bifidobacteria from Apis mellifera intermissa and its products

The present study aimed to evaluate the probiotic potential, α-amylase and α-glucosidase inhibitory effects, and β-galactosidase production of 19 non haemolytic lactic acid bacteria and bifidobacteria previously identified and isolated from honey bee gastrointestinal tract (BGIT) of Apis mellifera intermissa, honey, propolis and bee bread. The isolates were screened according to their high resistance to lysozyme and potent antibacterial activity. Our results indicated that among the 19 isolates, Limosilactobacillus fermentum BGIT_E12.2, Lactiplantibacillus plantarum BGIT_EC13, Limosilactobacillus fermentum BGIT_EC5.1 and Bifidobacterium asteroides BGIT_OB8, isolated from BGIT exhibited a good tolerance to 100 mg/mL lysozyme (> 82%), excellent tolerance to 0.5% bile salt [survival rate (SR) ≥ 83.19% ± 0.01], and a high SR (≥ 80.0%) under gastrointestinal tract conditions. The auto-aggregation ability was high (auto-aggregation index ranging from 67.14 ± 0.16 to 92.8% ± 0.03) for L. fermentum BGIT_E12.2, L. plantarum BGIT_EC13, and B. asteroides BGIT_OB8, and moderate for L. fermentum BGIT_EC5.1 (39.08% ± 0.11). Overall, the four isolates showed moderate co-aggregation capacity with pathogenic bacteria. They exhibited from moderate to high hydrophobicity towards toluene and xylene. The safety assessment revealed that the four isolates lacked gelatinase and mucinolytic activities. Also, they were susceptible to ampicillin, clindamycin, erythromycin, and chloramphenicol. Interestingly, the four isolates showed α-glucosidase and α-amylase inhibitory activities ranging from 37.08 ± 0.12 to 57.57% ± 0.1 and from 68.30 ± 0.09 to 79.42% ± 0.09, respectively. Moreover, L. fermentum BGIT_E12.2, L. plantarum BGIT_EC13, L. fermentum BGIT_EC5.1 isolates exhibited β-galactosidase activity over a wide range of 52.49 ± 0.24-746.54 ± 0.25 Miller Units. In conclusion, our findings suggest that the four isolates could be potential candidates for probiotics with interesting functional properties.

Screening and Characterization of Pediococcus acidilactici LC-9-1 toward Selection as a Potential Probiotic for Poultry with Antibacterial and Antioxidative Properties

Growing interest has been focused on lactic acid bacteria as alternatives to antimicrobial growth promoters, which are characterized by the production of various functional metabolites, such as antimicrobial and antioxidants compounds. The present study was undertaken to evaluate a potential probiotic from the antioxidant perspective. LC-9-1, screened from the intestines of healthy animals, was revealed to be Pediococcus acidilactici on the basis of its morphological, biochemical, and molecular characteristics. The strain has excellent properties, including acid-production efficiency, antibacterial performance and antioxidant activity. The safety of the strain was also evaluated. Furthermore, the experiments in broiler chickens suggested that dietary LC-9-1 supplementation improved the growth performance and decreased the abdominal fat, and enhanced the antioxidant capability and intestinal innate immunity of broilers. Analysis of intestinal microbiota showed that a higher community diversity (Shannon index) was achieved. In addition to the significantly increased relative abundances of Pediococcus spp., beneficial genera such as Rothia spp. and Ruminococcus spp. were abundant, while opportunistic pathogens such as Escherichia-Shigella spp. were significantly reduced in LC-9-1-supplemented broilers. Collectively, such in-depth characterization and the available data will guide future efforts to develop next-generation probiotics, and LC-9-1 could be considered a potential strain for further utilization in direct-fed microbial or starter culture for fermentation.

Composition and factors influencing community structure of lactic acid bacterial in dairy products from Nyingchi Prefecture of Tibet

This study investigated the community composition of lactic acid bacteria (LAB) from yaks' milk (YM) Tibetan yellow cattle milk (TM) and their fermented products from different counties in the Nyingchi Prefecture, Tibet using Pacific Biosciences (PacBio) single-molecule real-time (SMRT) sequencing. Sequencing revealed 26 genera and 94 species from 71 dairy samples; amongst these Lactobacillus delbrueckii (36.17%), Streptococcus thermophilus (19.46%) and Lactococcus lactis (18.33%) were the predominant species. This study also identified the main factors influencing LAB community composition by comparing amongst samples from different locations, from different milk types, and from different altitudes. The LAB communities in YM and TM were more diverse than in fermented yaks' milk (FYM) and fermented Tibetan yellow cattle milk (FTM) samples. Similarly, whether milk was fermented or not accounted for differences in LAB species composition while altitude of the dairy products had very little effect. Milk source and production process were the most likely causes of drastic shifts in microbial community composition. In addition, fermented dairy products were enriched in genes responsible for secondary metabolic pathways that were potentially beneficial for health. Comprehensive descriptions of the microbiota in different dairy products from the Nyingchi Prefecture, Tibet might help elucidate evolutionary and functional relationships amongst bacterial communities in these products.

Lactiplantibacillus plantarum A1, C1 and C10 Are Potential Probiotics Isolated from Pineapple Residual Silage

The production and consumption of pineapple creates large quantities of residues. Ensiling these residues might help to minimize the waste burden and meet the intensive feed demand for ruminants. Proper lactic acid bacteria (LAB) are not only responsible for pineapple residual silage fermentation, but might also deliver probiotics. The aim of this study was to isolate LAB strains with probiotic functions, and to enhance intestinal antioxidant capacity from naturally fermented pineapple residues. A total of 47 LAB isolates with gram-positive, catalase-negative, nonhemolytic properties were used for probiotic screening. Lactiplantibacillus plantarum (L. plantarum) A1, C1 and C10 were susceptible to rifampicin, gentamicin and erythromycin, did not contain virulence factor-coding genes and showed good tolerance to acid (pH 3.0), 0.5% bile salt and simulated gastric and intestinal fluid. Their hydrophobicity indices were 71.92%, 45.50% and 66.90%, respectively. All of them were able to adhere to bovine jejunum epithelial cells (BJECs) and to antagonize Escherichia coli F5 and Salmonella Dublin. These three LAB strains tolerated hydrogen peroxide and significantly decreased (p < 0.05) reactive oxygen species levels in BJECs. In addition, L. plantarum C1 and C10 significantly increased (p < 0.05) the total antioxidant capacity in BJECs in the presence of 200 μmol/L hydrogen peroxide condition. L. plantarum A1, C1 and C10 are potential probiotics isolated from pineapple residual silage. This study aims to promote pineapple residue’s utilization in the feed industry.

Colicins of Escherichia coli Lead to Resistance against the Diarrhea-Causing Pathogen Enterotoxigenic E. coli in Pigs

Gut microbes can affect host adaptation to various environment conditions. Escherichia coli is a common gut species, including pathogenic strains and nonpathogenic strains. This study was conducted to investigate the effects of different E. coli strains in the gut on the health of pigs. In this study, the complete genomes of two E. coli strains isolated from pigs were sequenced. The whole genomes of Y18J and the enterotoxigenic E. coli strain W25K were compared to determine their roles in pig adaptation to disease. Y18J was isolated from feces of healthy piglets and showed strong antimicrobial activity against W25K in vitro. Gene knockout experiments and complementation analysis followed by modeling the microbe-microbe interactions demonstrated that the antagonistic mechanism of Y18J against W25K relied on the bacteriocins colicin B and colicin M. Compared to W25K, Y18J is devoid of exotoxin-coding genes and has more secondary-metabolite-biosynthetic gene clusters. W25K carries more genes involved in genome replication, in accordance with a shorter cell cycle observed during a growth experiment. The analysis of gut metagenomes in different pig breeds showed that colicins B and M were enriched in Laiwu pigs, a Chinese local breed, but were scarce in boars and Duroc pigs. IMPORTANCE This study revealed the heterogeneity of E. coli strains from pigs, including two strains studied by both in silico and wet experiments in detail and 14 strains studied by bioinformatics analysis. E. coli Y18J may improve the adaptability of pigs toward disease resistance through the production of colicins B and M. Our findings could shed light on the pathogenic and harmless roles of E. coli in modern animal husbandry, leading to a better understanding of intestinal-microbe-pathogen interactions in the course of evolution.

Characterization of potential probiotic bacteria Enterococcus faecium MC-5 isolated from the gut content of Cyprinus carpio specularis

The goal of this study was to determine the unique characteristics of Enterococcus faecium MC-5, a probiotic bacteria isolated from the intestine of a fish, Cyprinus carpio specularis, collected from Dal Lake in Srinagar, Kashmir, India. For this, the important valuable probiotic attributes, some functional properties, and safety assessments were analyzed in-vitro for the strain MC-5. The strain E. faecium MC-5 exhibited high resistance to low pH, high bile salt, lysozyme, and phenol. The strain MC-5 showed excellent auto- and co-aggregation properties and displayed remarkable hydrophobicity towards various tested hydrocarbons which suggested that the strain possesses venerable adhesion properties. Apart from these, the cell-free supernatant (CFS) of strain MC-5 exhibited phenomenal antimicrobial activity against the tested pathogens. A scanning electron microscope (SEM) image revealed strain MC-5 finely adhered to human colon adenocarcinoma cells (HCT-15 cells). The strain MC-5 showed high bile salt hydrolase activity and excellent cholesterol removal ability of 70.27%. The intact cells of strain MC-5 also showed strong DPPH scavenging activity. The EPS produced by E. faecium MC-5 inhibited the adhesion of Listeria monocytogenes, Staphylococcus aureus, and Salmonella enterica on HCT-15 cells with maximum inhibition rates of 41.82, 40.34, and 55.51%, respectively for displacement assay, which was higher as compared to exclusion (26.06, 26.11, and 39.23%) and competition assays (30.06, 26.7, and 41.20%). Strain MC-5 did not exhibit hemolysis and was also found susceptible to vancomycin and other clinically important antibiotics. When evaluating all the results from the present study, it is propounded that strain MC-5 has enviable probiotic characteristics and thus can be used as bio-protective cultures and/or bio-shield in food and pharmaceutical industries.

Screening and evaluation of lactic acid bacteria with probiotic potential from local Holstein raw milk

There are massive bacteria in the raw milk, especially the lactic acid bacteria (LABs), which have been considered probiotics in humans and animals for a long time. Novel probiotics are still urgently needed because of the rapid development of the probiotic industry. To obtain new LABs with high probiotic potential, we obtained 26 LAB isolates, named L1 ~ L26, from local Holstein raw milk collected from a farm whose milk had never been used for LAB isolation. We identified them at the species level by biochemical and 16S rDNA sequencing methods. Their antagonistic activities against four target pathogens (Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa PAO1, and Salmonella enterica H9812), co-aggregative ability with these target pathogens, survivability in the simulated gastrointestinal tract conditions and phenol, auto-aggregation and hydrophobicity, hemolytic activity, and antibiotic susceptibility, were evaluated in vitro. Five Lactiplantibacillus plantarum isolates (L5, L14, L17, L19, and L20) showed more promising probiotic potential than others. Specifically, these five isolates conglutinated with and inhibited all the target pathogens, and survived in the simulated gastric juice (92.55 ~ 99.69%), intestinal juice (76.18 ~ 83.39%), and 0.4% phenol (76.95 ~ 88.91%); possessed considerable auto-aggregation (83.91 ~ 90.33% at 24 h) and hydrophobicity (79.32 ~ 92.70%); and were non-hemolytic, sensitive to kinds of common antimicrobials. Our findings demonstrated that these five isolates could be preliminarily determined as probiotic candidates because they have better probiotic potential than those previously reported. Again, this study highlighted the potential of raw milk for probiotic isolating and screening and provided the probiotic industry with five new LAB candidates.

Mapping the global research landscape on nutrition and the gut microbiota: Visualization and bibliometric analysis

BACKGROUND

Nutrition is a significant modifiable element that influences the composition of the gastrointestinal microbiota, implying the possibility of therapeutic diet methods that manipulate the composition and diversity of the microbial.

AIM

To overview research papers on nutrition and gut microbiota and determines the hotspots in this field at the global level.

METHODS

Scopus and Reference Citation Analysis were used to construct a bibliometric technique. It was decided to create bibliometric indicators and mapping as in most previous studies. 2012 through 2021 served as the study's timeframe.

RESULTS

A total of 5378 documents from the Scopus database were selected for analysis. Of all retrieved studies, 78.52% were research papers (n = 4223), followed by reviews (n = 820; 15.25%). China ranked first with a total number of articles of 1634 (30.38%), followed by the United States in second place with a total number of articles of 1307 (24.3%). In the last decade, emerging hotspots for gut microbiota and nutrition research included "gut microbiota metabolism and interaction with dietary components", "connection between the gut microbiota and weight gain", and "the influence of high-fat diet and gut microbiota on metabolic disorders".

CONCLUSION

This is the first thorough bibliometric analysis of nutrition and gut microbiota publications conducted on a global level. Investigation of the association between nutrition/diet and the gut microbiota is still in its infancy and will be expanded in the future. However, according to recent trends, the “effect of gut microbiota and high-fat diet on metabolic disorders" will be an increasing concern in the future.

Bacteriocin-Producing Lactic Acid Bacteria Strains with Antimicrobial Activity Screened from Bamei Pig Feces

Lactic acid bacteria (LAB), which are characterized by producing various functional metabolites, including antioxidants, organic acids, and antimicrobial compounds, are widely used in the food industry to improve gut health and prevent the growth of spoilage microorganisms. With the continual incidence of foodborne disease and advocacy of consumers for gut health, LAB have been designated as vital biopreservative agents in recent years. Therefore, LAB with excellent antimicrobial properties and environmental tolerance should be explored further. In this study, we focus on screening the LAB strains from a specialty pig (Bamei pig) feces of the Tibetan plateau region and determine their antimicrobial properties and environmental tolerance to evaluate their potential probiotic values. A total of 116 LAB strains were isolated, from which the LAB strain Qinghai (QP)28-1 was identified as Lactiplantibacillus (L.) plantarum subsp. plantarum using 16S rDNA sequencing and recA amplification, showing the best growth capacity, acid production capacities, environmental tolerance, hydrophobicity, antibiotic susceptibility, and bacteriocin production capacity. Furthermore, this strain inhibited the growth of multiple pathogens by producing organic acids and bacteriocin. These bacteriocin-encoding genes were identified using PCR amplification, including plnS, plnN, and plnW. In conclusion, bacteriocin-producing L. plantarum subsp. plantarum QP28-1 stands out among these 116 LAB strains, and was considered to be a promising strain used for LAB-related food fermentation. Moreover, this study provides a convenient, comprehensive, and shareable profile for screening of superior functional and bacteriocin-producing LAB strains, which can be used in the food industry.

In-Vitro Characterization of Growth Inhibition against the Gut Pathogen of Potentially Probiotic Lactic Acid Bacteria Strains Isolated from Fermented Products

Lactic acid bacteria (LAB) are probiotic candidates that may restore the balance of microbiota populations in intestinal microbial ecosystems by controlling pathogens and thereby promoting host health. The goal of this study was to isolate potential probiotic LAB strains and characterize their antimicrobial abilities against pathogens in intestinal microbiota. Among 54 LAB strains isolated from fermented products, five LAB strains (NSMJ15, NSMJ16, NSMJ23, NSMJ42, and NFFJ04) were selected as potential probiotic candidates based on in vitro assays of acid and bile salt tolerance, cell surface hydrophobicity, adhesion to the intestinal epithelium, and antagonistic activity. Phylogenetic analysis based on 16S rRNA genes showed that they have high similarities of 99.58-100% to Lacticaseibacillus&nbsp;paracasei strains NSMJ15 and NFFJ04, Lentilactobacillus parabuchneri NSMJ16, Levilactobacillus&nbsp;brevis NSMJ23, and Schleiferilactobacillus harbinensis NSMJ42. To characterize their antimicrobial abilities against pathogens in intestinal microbiota, the impact of cell-free supernatant (CFS) treatment in 10% (v/v) fecal suspensions prepared using pooled cattle feces was investigated using in vitro batch cultures. Bacterial community analysis using rRNA amplicon sequencing for control and CFS-treated fecal samples at 8 and 16 h incubation showed the compositional change after CFS treatment for all five LAB strains. The changed compositions were similar among them, but there were few variable increases or decreases in some bacterial groups. Interestingly, as major genera that could exhibit pathogenicity and antibiotic resistance, the members of Bacillus, Escherichia, Leclercia, Morganella, and Vagococcus were decreased at 16 h in all CFS-treated samples. Species-level classification suggested that the five LAB strains are antagonistic to gut pathogens. This study showed the probiotic potential of the five selected LAB strains; in particular, their antimicrobial properties against pathogens present in the intestinal microbiota. These strains would therefore seem to play an important role in modulating the intestinal microbiome of the host.

Genomic and proteomic comparisons of bacteriocins in probiotic species Lactobacillus and Bifidobacterium and inhibitory ability of Escherichia coli MG 1655

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The genomes and proteomes of 12 Bifidobacterium and 46 Lactobacillus were reviewed and then compared for bacteriocin identification.

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NCBI-Genome, UniProt-Proteome, Bactibase, and BAGL4 databases, as well as BLASTP, and Clustal Omega can be used for bacteriocin mining.

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Lactobacillus species have more diversity and abundance of bacteriocin compared to Bifidobacterium species.

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Notably, L. sakei, L. plamtarum, L. reuteri, L. fermentum, and L. casei had the highest pathogen inhibition (E. coli MG 1655); respectively.

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A set of Lactobacillus bacteria including L. sakei, L. reuteri, L. fermentum, and L. casei can be proposed as a biosecure and safe solution to control gastrointestinal pathogens.

Bacteriocins are a large family of bacterial peptides or proteins, ribosomally synthesized with antimicrobial activity against other bacteria. We investigated and compared the genomes and proteomes of 12 Bifidobacterium and 46 Lactobacillus species for bacteriocins using NCBI-Genome, UniProt-Proteome, Bactibase, and BAGL4 databases. Selected Lactobacillus species were examined for bile salt resistance, acid and pH resistance, pepsin and trypsin enzyme resistance, and antibiotic resistance. Also, the antimicrobial activity of selected Lactobacillus species was evaluated against E. coli MG 1655. Results showed that Lactobacillus species have more diversity and abundance of bacteriocin compared to Bifidobacterium species. Notably, L. sakei, L. plamtarum, L. reuteri, L. fermentum, and L. casei had the highest pathogen inhibition; respectively. Therefore, a combination of these Lactobacillus species can be suggested as a biochemical and safe solution to control gastrointestinal pathogens and suitable alternatives to antibiotics and chemicals in food technology.

Probiotic Potential and Wide-spectrum Antimicrobial Activity of Lactic Acid Bacteria Isolated from Infant Feces

In this study, we aimed to characterize lactic acid bacteria strains derived from infants' feces, to evaluate the probiotic potential and explore the wide-spectrum antimicrobial activity. Of 800 isolates, 20 inhibited the growth of enterotoxigenic Escherichia coli K88 and Salmonella enterica ATCC 13076. On the basis of 16S rRNA sequence analysis, the 20 isolates were assigned to Lactobacillus casei (7), Lactobacillus paracasei (2), Lactobacillus plantarum (4), Lactobacillus rhamnosus (2), Enterococcus avium (3), Enterococcus faecium (1), and Enterococcus lactis (1) species. In addition, 12 strains with high antimicrobial activity were investigated for the presence of probiotic properties such as physiological-biochemical characteristics, antimicrobial susceptibility, hemolytic activity, hydrophobicity, and aggregation activity. Wide-spectrum antimicrobial activity analysis revealed that approximately all tested strains inhibited the ten pathogens, and four strains (ZX221, ZX633, ZX3131, and ZX3875) had good probiotic properties and survived after being exposed to simulated gastrointestinal tract conditions. Moreover, we investigated the influence of pH on the wide-spectrum antimicrobial activity and found that four strains inhibited most pathogens at pH 4.5 and pH 5, whereas only ZX633 had an inhibitory effect on Bacillus subtilis ATCC 6633 and Micrococcus luteus ATCC 4698 at pH 5.5. Overall, Lact. casei ZX633 had wide-spectrum antimicrobial activity and could be considered a potential probiotic.

Screening of Probiotic Lactic Acid Bacteria Isolated from Fermented Pak-Sian for Use as a Starter Culture

The objective of this research was to evaluate the probiotic properties of lactic acid bacteria (LAB) isolated from fermented Pak-Sian, a traditional Thai food in the northeastern region of Thailand (Kalasin, Sakon Nakhon, Maha Sarakham, and Khon Kaen Provinces). A total of 61 LAB isolates isolated from selective MRS agar were screened by SDS-PAGE and identified by 16S rDNA analysis. Seventeen bacterial strains were found consisting of Pediococcus pentosaceus (6 strains) Lactiplantibacillus plantarum (5 strains), Levilactobacillus brevis (1 strain), Lactobacillus fermentum (3 strains), and Weissella cibaria (2 strains). A PH tree grouped 17 LAB strains into 5 clusters with three clusters only recorded from Sakon Nakhon Province. All strains were tested for probiotic properties. Results showed that 14 strains had the ability to resist pH 2.5 as resistant to bile salts and survive in gastric juices and the intestinal tract. LAB demonstrated antimicrobial activity against 4 pathogens: Staphylococcus aureus TISTR746, Salmonella typhimurium TISTR1472, Escherichia coli ATCC25922, and Bacillus cereus TISTR1449. Most LAB strains were resistant to all antibiotics tested, while some Lactobacillus strains were moderately susceptible to chloramphenicol, rifampicin, and ampicillin. None of the 14 strains produced biogenic amine and eight showed no hemolysis activity, indicating the safety of these strains. These 8 strains were selected to determine mucin adhesion capacity. Lactobacillus fermentum SK324 and Levilactobacillus brevis SK335 showed the highest adhesion capacity of 2.39 and 2.34%, respectively. These two strains showed promise as alternative starter cultures to improve probiotic health benefits of local fermented Pak-Sian products as a functional food.

Antibacterial Activity of Lactic Acid Producing Leuconostoc mesenteroides QZ1178 Against Pathogenic Gallibacterium anatis

Lactic acid bacteria (LAB) convert carbohydrates into organic acids [mainly lactic acid (LA)], which reportedly have bactericidal activities. Gallibacterium anatis is a Gram-negative bacteria which infects birds, and causes significant economic losses. In this study, we investigated the antibacterial activity of the LA producing, Leuconostoc mesenteroides QZ1178 from Qula (fermented food), against G. anatis, using the Oxford cup method. Our data showed that L. mesenteroides QZ1178 inhibited G. anatis isolates from different origins; however, L. mesenteroides QZ1178 antibacterial activity dropped dramatically at pH 5.5–pH 6. The LA concentration and pH of the liquid broth containing L. mesenteroides QZ1178 after 24 h culture was 29 mg/mL and 3.6, respectively. This concentration (29 mg/mL at pH 3.6) and the antibiotic, cefotaxime (minimum inhibitory concentration (MIC) 2.5 μg/mL) effectively inhibited G. anatis (GAC026) growth as observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Gallibacterium anatis treated with LA exhibited extensive cell surface collapse, increased cell damage, cell membrane disruption, and cytoplasmic leakage, indicative of cell lysis. We suggest L. mesenteroides QZ1178 exerts potential antibacterial effects against the poultry pathogen, G. anatis via LA.

In vitro properties of potential probiotic lactic acid bacteria originating from Ghanaian indigenous fermented milk products

Fermented milk products are a major source of health-promoting microorganisms known as probiotics. To characterize the probiotic properties of lactic acid bacteria isolated from Ghanaian traditionally fermented milk, thirty (30) isolates comprising Enterococcus faecium (1), Lactobacillus fermentum (14), Lb. plantarum (2) and Pediococcus acidilactici (13) identified by 16S rRNA gene sequencing, were tested for survival at low pH (2.5) and bile salts (0.3% (w/v)), hydrophobicity, co-aggregation, auto-aggregation and antimicrobial activities against selected pathogens. Safety of potential probiotic bacteria was assessed by hemolytic activity on blood agar and susceptibility to nine different antibiotics. Majority (90%) of the strains showed survival rates above 80% at pH (2.5) and in bile salts (0.3% (w/v)). Hydrophobicity ranged from 5 to 61% while cell auto-aggregation ranged from 41 to 80% after 24 h. Co-aggregation with E. coli (3.7-43.9%) and S. Typhimurium (1.3-49.5%) were similar for the LAB strains at 24 h. Cell- free supernatants of all LAB strains inhibited E. coli while S. Typhimurium was not sensitive to cell-free supernatants of five Pd. acidilactici strains: OS24h20, OS18h3, OY9h19, OS9h8 and 24NL38. None of the LAB strains showed β-hemolysis but 38% of strains showed α-hemolysis. Susceptibilities to antibiotics were strain-specific; only four strains, two Lb. fermentum and two Pd. acidilactici were susceptible to all nine antibiotics tested. Based on high survival rates in bile salts, low pH and generally good hydrophobicity, auto-aggregation, co-aggregation and inhibitory activities, 15 out of 30 strains tested were considered qualified candidates for development of probiotic cultures for fermented milk products in sub-Saharan Africa.

Multilocus Sequence Typing of Leuconostoc mesenteroides Strains From the Qinghai-Tibet Plateau

Leuconostoc mesenteroides strains were a type of epiphytic bacterium widely used in fermented foods and products in the biochemical and pharmaceutical industries but data on its presence in foods from Qinghai-Tibet Plateau in China was scarce. In this study, molecular analysis based on multilocus sequence typing (MLST) with eight housekeeping genes (pyrG, groeL, rpoB, recA, uvrC, murC, carB, and pheS) was carried out on 45 L. mesenteroides strains isolated from different plants and dairy products from Qinghai-Tibet Plateau in China. The objective of this study was to perform genetic diversity analysis and explore the relationship between strains and isolate samples or separate regions. A total of 25 sequence types (STs) were identified with a diversity of up to 55.6%, which were grouped into one clonal complexes (CCs), 3 doublets and 17 singletons by eBURST. The results of minimum spanning tree and clustering analysis indicated these L. mesenteroides strains from the Qinghai-Tibet Plateau were relatively weakly related to the isolated region. However, there was a close relationship between the genotypes of L. mesenteroides strains and the type of the isolated sample, which was consistent with the results of API 50CH. The MLST scheme presented in this study provides a shareable and comparable sequence database and enhances our knowledge of the population diversity of L. mesenteroides strains which will be further used for the selection of industrial strains.

Isolation of Bile Salt Hydrolase and Uricase Producing Lactobacillus brevis SF121 from Pak Sian Dong (Fermented Spider Plant) for using as Probiotics

The interesting application of bile salt hydrolase enzyme is reduction of cholesterol in serum and amelioration lipid profile. While uricase enzyme can be applied to convert insoluble uric acid to be soluble form and excrete from the body. Probiotics are living organisms with generally know that they can provide beneficial effects to their host. Several reports show that probiotic bacteria with bile salt hydrolase and uricase can improve hypercholesterolemia and hyperuricemia patient. The novel isolate of Lactobacillus from Pak Sian Dong in this study is identified as L. brevis SF121 and probably use as probiotic bacteria in the future. However, this isolate still need further experiments to investigate and improve properties of probiotics. Moreover, this finding suggests that Pak Sian Dong or fermented spider plant can be designated as a good source for probiotic screening and also defines as health-promoting diet.

The in vitro Effects of the Probiotic Strain, Lactobacillus casei ZX633 on Gut Microbiota Composition in Infants With Diarrhea

We investigated the in vitro effects of Lactobacillus casei ZX633 on gut microorganism composition in infants with diarrhea. For this purpose, 103 feces samples from healthy infants (healthy group) and 300 diarrhea samples from infants (diarrhea group) were collected, and diarrhea feces were treated with L. casei ZX633, which was previously isolated from healthy infant feces (treatment group). We used microbial dilution plate methods, high performance liquid chromatography (HPLC) and high-throughput sequencing approaches to analyze viable main microorganism counts, short chain fatty acid (SCFA) concentrations, and intestinal microbiota composition in feces, respectively. Our data showed that L. casei ZX633 supplementation increased the numbers of Escherichia coli, yeasts, lactic acid bacteria (LAB) and aerobic-bacteria, raised propionic acid levels but reduced four other SCFAs, which are close to the healthy group. Alpha diversity results indicated that microbial diversity and richness decreased in treatment group. Bacterial community analyses revealed that microbial structures of the treatment group tended toward the healthy group; i.e., Escherichia-Shigella and Clostridioides abundance increased, and there was a reduction in the abundance of Streptococcus, Bacteroides, Enterococcus and Veillonella. In conclusion, L. casei ZX633 isolated from healthy infant feces, may be effective in improving infant diarrhea microbiota, potentially providing a new probiotic strain to reduce the incidence of diarrhea associated with bacterial disease in infants.

Functional probiotics of lactic acid bacteria from Hu sheep milk

Background

Probiotics are being considered as valuable microorganisms related to human health. Hu sheep is referred as one of the important sheep breeds in China. Goat milk produced by Hu sheep is characterized with high nutritional value and hypoallergenic in nature. Particularly, this milk contains plenty of milk prebiotic and probiotic bacteria. This study was aimed to scrutinize more bacterial strains from Hu sheep milk with potential probiotic activity.

Results

Based on 16S rRNA sequence analysis, pool of forty bacterial strains were identified and evaluated their antimicrobial activities against Staphylococcus aureus, enterohemorrhagic Escherichia coli (EHEC), Salmonella typhimurium, Listeria monocytogenes enterotoxigenic E. coli (ETEC) and Aeromonas caviae. Four out of these isolated strains demonstrated their efficient bacteriostatic ability and potential healthy properties. We also examined the safety aspects of these bacterial candidates including three Lactococcus lactis strains (named as HSM-1, HSM-10, and HSM-18) and one Leuconostoc lactis strain (HSM-14), and were further evaluated via in vitro tests, including antimicrobial activity, cell surface characteristics (hydrophobicity, co-aggregation, and self-aggregation), heat treatment, antibiotic susceptibility, simulated transport tolerance in the gastrointestinal tract, and acid/bile tolerance. The obtained results revealed that HSM-1, HSM-10, HSM-14, and HSM-18 showed high survival rate at different conditions for example low pH, presence of bovine bile and demonstrated high hydrophobicity. Moreover, HSM-14 had an advantage over other strains in terms of gastrointestinal tract tolerance, antimicrobial activities against pathogens, and these results were significantly better than other bacterial candidates.

Conclusion

Hu sheep milk as a source of exploration of potential lactic acid bacteria (LAB) probiotics open the new horizon of probiotics usage from unconventional milk sources. The selected LAB strains are excellent probiotic candidates which can be used for animal husbandry in the future. Rationale of the study was to utilize Hu sheep milk as a source of potential probiotic LABs. The study has contributed to the establishment of a complete bacterial resource pool by exploring the Hu sheep milk microflora.

Milk Products from Minor Dairy Species: A Review

Milk processing is one of the most ancient food technologies, dating back around 6000 BC. The majority of dairy products are manufactured from cows, buffaloes, goats, and sheep; their production technologies are mostly standardized and have been widely investigated. Milk and dairy products from minor species are less important under the economic point of view, but they play a fundamental social role in many marginal and poor areas. Due to scarce interest of the dairy industry, their technological characteristics and related issues have been investigated less. Recently, the increasing interest toward ethnic foods and food biodiversity is helping these minor products to emerge from the "darkness" in which they have remained for long time. Some of them are increasingly seen as useful for the valorization of marginal areas, while others are recognized as innovative or healthy foods. The present review aims to resume the most recent knowledge about these less-known dairy products. The first part summarizes the main technological properties of equine, camel, and yak milk with a view to processing. The second is a survey on the related dairy products, both the traditional ones that have been manufactured for a long time and those that have been newly developed by food researchers.

A critical review of antibiotic resistance in probiotic bacteria

Probiotics are defined as live microorganisms that, when administered in adequate amounts, confer a health benefit upon the host. At present, probiotics are gaining popularity worldwide and are widely used in food and medicine. Consumption of probiotics is increasing with further in-depth research on the relationship between intestinal flora and host health. Most people pay more attention to the function of probiotics but ignore their potential risks, such as infection and antibiotic resistance transfer to pathogenic microbes. Physiological functions, effects and mechanisms of action of probiotics were covered in this review, as well as the antibiotic resistance phenotypes, mechanisms and genes found in probiotics. Typical cases of antibiotic resistance of probiotics were also highlighted, as well as the potential risks (including pathogenicity, infectivity and excessive immune response) and corresponding strategies (dosage, formulation, and administration route). This timely study provides an avenue for further research, development and application of probiotics.

Low-Carbohydrate Tolerant LAB Strains Identified from Rumen Fluid: Investigation of Probiotic Activity and Legume Silage Fermentation

The objective of this study was to isolate and characterize lactic acid bacteria (LAB) with low carbohydrate tolerance from rumen fluid and to elucidate their probiotic properties and the quality of fermentation of Medicago sativa L. and Trifolium incarnatum L. silage in vitro. We isolated 39 LAB strains and screened for growth in MRS broth and a low-carbohydrate supplemented medium; among them, two strains, Lactiplantibacillus plantarum (Lactobacillus plantarum) RJ1 and Pediococcus pentosaceus S22, were able to grow faster in the low-carbohydrate medium. Both strains have promising probiotic characteristics including antagonistic activity against P. aeruginosa, E. coli, S. aureus, and E. faecalis; the ability to survive in simulated gastric-intestinal fluid; tolerance to bile salts; and proteolytic activity. Furthermore, an in vitro silage fermentation study revealed that alfalfa and crimson clover silage inoculated with RJ1 and S22 showed significantly decreased pH and an increased LAB population at the end of fermentation. Also, the highest lactic acid production was noted (p < 0.05) in LAB-inoculated silage vs. non-inoculated legume silage at high moisture. Overall, the data suggest that RJ1 and S22 could be effective strains for fermentation of legume silage.

Isolation and identification of potential probiotic Lactobacillus species from feces of infants in southwest Iran

OBJECTIVES

To evaluate the potential probiotic properties of Lactobacillus strains isolated from feces of infants and also to determine their antimicrobial activity against some enteropathogenic bacteria.

METHODS

The Fecal samples were prepared from 120 infants aged less than 24 months. In total, 105 Lactobacillus strains were identified by phenotypic tests. Thirty isolates were randomly selected to study their potential probiotic properties. These isolates were examined for resistance to acid (pH: 2.5, 2 h) and bile (oxgall 0.3%, 8 h), adhesion to HT-29 cells, antibiotic susceptibility, and antimicrobial activities.

RESULTS

On basis of 16S rRNA sequencing, 30 isolates identified as Lactobacillus fermentum (n = 11; 36.7%), Lactobacillus plantarum (n = 9; 30%), Lactobacillus rhamnosus (n = 6; 20%), and Lactobacillus paracasei (n = 4; 13.3%). All tested strains survived at acid and bile conditions. Six Lactobacillus strains revealed high adherence to HT-29 cells. Three strains including the L. fermentum (N2, N7), and the L. plantarum (N20) showed good probiotic potential and inhibited the growth of Yersinia enterocolitica ATCC 23715, Shigella flexneri ATCC 12022, Salmonella enterica ATCC 9270, and enteropathogenic Escherichia coli (EPEC) ATCC 43887. The antibiotic resistance test showed that all the isolates were susceptible to tetracycline, and chloramphenicol.

CONCLUSIONS

Lactobacillus strains like L. fermentum (N2, N7), and the L. plantarum (N20), could be potential probiotic, but further in vitro and in vivo studies on these probiotic strains are still required.

Isolation, characterization and anti-inflammatory mechanism of probiotics in lipopolysaccharide-stimulated RAW 264.7 macrophages

Probiotics are known to modulate gut microbiota, intestinal barrier function and host immune response, but due to the species and strain specific response their mechanisms are not clearly understood. Thus, the present study was designed to isolate, assess the anti-inflammatory potential and underlying modulatory mechanisms of indigenous probiotics in murine macrophage cell line, RAW 264.7. Forty lactic acid bacteria (LAB) were isolated from different sources and monitored for their anti-inflammatory potential against lipopolysaccharide (LPS) induced inflammatory stress employing RAW 264.7 cells. Among these isolates, only four LAB isolates exhibited more than 90% nitric oxide inhibition and possessed the probiotic attributes. Further, these selected LAB isolates reduced the level of pro-inflammatory cytokines, TNF-α, IL-1β and IL-6, inhibited the phosphorylation of Mitogen Activated Protein Kinases (MAPKs) i.e. p38 MAPK, ERK1/2 and SAPK/JNK and expression of cyclooxygenase-2 (COX-2) in LPS stimulated RAW 264.7 cells. The in vitro analysis suggested that the selected probiotic isolates attenuated the LPS-induced inflammation by downregulating MAPK pathway vis-a-vis inhibiting COX-2 and can be employed as anti-inflammatory agents in various inflammatory diseases.

In Vitro Study of Immune Properties of New Lactobacilli Isolates from Pheasant Gut

The goal of this paper was to study the effect of Lactobacillus reuteri B1/1, B2/1 and B6/1 on the relative expression of selected interleukins (IL-1β, IL-15), macrophage inflammatory protein (MIP-1β), and the relative percentage of T lymphocyte subpopulations in peripheral mononuclear blood cells (PMBCs). The mRNA expression levels of interleukins and MIP-1β of PMBCs were evaluated at 24 h and 48 h post inoculation using the quantitative real-time polymerase chain reaction (qRT-PCR). The percentage of T lymphocyte subpopulations in PMBCs was determined by flow cytometry. The group that was administered L. reuteri B1/1 had the most significant stimulation of the expression of pro-inflammatory interleukins and MIP-1β, in particular after 24 h. Similarly, we observed a rise in the relative percentage of T cells including CD3+, CD4+ and CD8+ lymphocytes in the groups with L. reuteri B1/1 and L. reuteri B2/1. Overall, L. reuteri B1/1 and L. reuteri B2/1 showed a promising stimulatory effect on the relative expression of pro-inflammatory interleukins, MIP-1β and percentage of T cell subpopulations in vitro. On the flip side, L. reuteri B6/1 did not induce the expression of the IL-1β gene.

Identification of salt tolerance-related genes of Lactobacillus plantarum D31 and T9 strains by genomic analysis

Purpose

The aim of this study was to identify salt tolerance-related genes of Lactobacillus plantarum D31 and T9 strains, isolated from Chinese traditional fermented food, by genomic analysis.

Methods

Tolerance of L. plantarum D31 and T9 strains was evaluated at different stress conditions (temperatures, acid, osmolality, and artificial gastrointestinal fluids). Draft genomes of the two strains were determined using the Illumina sequencing technique. Comparative genomic analysis and gene transcriptional analysis were performed to identify and validate the salt tolerance-related genes.

Results

Both L. plantarum D31 and T9 strains were able to withstand high osmotic pressure caused by 5.0% NaCl, and L. plantarum D31 even to tolerate 8.0% NaCl. L. plantarum D31 genome contained 3,315,786 bp (44.5% GC content) with 3106 predicted protein-encoding genes, while L. plantarum T9 contained 3,388,070 bp (44.1% GC content) with 3223 genes. Comparative genomic analysis revealed a number of genes involved in the maintenance of intracellular ion balance, absorption or synthesis of compatible solutes, stress response, and modulation of membrane composition in L. plantarum D31 and or T9 genomes. Gene transcriptional analysis validated that most of these genes were coupled with the stress-resistance phenotypes of the two strains.

Conclusions

L. plantarum D31 and T9 strains tolerated 5.0% NaCl, and D31 even tolerated 8.0% NaCl. The draft genomes of these two strains were determined, and comparative genomic analysis revealed multiple molecular coping strategies for the salt stress tolerance in L. plantarum D31 and T9 strains.

Quorum quenching potential of Enterococcus faecium QQ12 isolated from gastrointestinal tract of Oreochromis niloticus and its application as a probiotic for the control of Aeromonas hydrophila infection in goldfish Carassius auratus (Linnaeus 1758)

Quorum quenching (QQ), the obstruction of quorum sensing, is the most attractive way to break down the N-acyl-homoserine lactones (AHL) molecules. This work was focused at isolating AHL degrading bacteria from gastrointestinal tract of Oreochromis niloticus, with abilities appropriate for use as probiotic in aquaculture. The presence of an autoinducer inactivation (aiiA) homolog gene and AHL inactivation assay showed that Enterococcus faecium QQ12, which was one among the 20 isolates, could rapidly degrade synthetic C6-HSL in vitro and hampered violacein production by Chromobacterium violaceum. It had excellent biodegrading ability of natural N-AHL produced by Aeromonas hydrophila, suggesting that it can be used as a potential quencher bacterium for disrupting the virulence of A. hydrophila. It was susceptible to all the five antibiotics tried out. The isolate grew well at pH 3.0-7.0, was resistant to high level of bile salts (0-0.9%) and 0.5% of phenol. QQ12 also exhibited high degree of auto-aggregation and co-aggregation, confirming that it possessed good probiotic attributes. Goldfish fed diet incorporated with 10⁸ and 10¹⁰ CFU g^-1 of the QQ12 for 30 days showed 76.66-86.66% survival when challenged with A. hydrophila. The study indicates that Enterococcus faecium QQ12 could be used as a non-antibiotic feed additive in aquaculture to control bacterial diseases.

Screening of Host Specific Lactic Acid Bacteria Active Against Escherichia coli From Massive Sample Pools With a Combination of in vitro and ex vivo Methods

A novel three-step combination of in vitro and ex vivo screening was established to massively screen host derived lactic acid bacteria (LAB) from the broiler chicken intestine with inhibitory activity against Escherichia coli. In a first step, a massive sample pool consisting of 7102 broiler-derived colonies from intestinal contents were established and sub-cultured. Supernatants thereof were incubated with an E. coli model strain to screen suitable isolates with inhibitory activity. A total of 76 isolates of interest were subsequently further studied based on either pH dependent or -independent activity in the second step of the assay. Here, in-depth growth inhibition of the E. coli model strain and the potential of isolates for lactic acid production as inhibitory substance were indexed for all isolates. Resulting scatter plots of both parameters revealed five isolates with exceptional inhibitory activity that were further studied under ex vivo condition in the third step of the assay. These isolates were taxonomically classified as strains of the species Lactobacillus agilis, Lactobacillus salivarius, and Pediococcus acidilactici. Samples from the broiler chicken intestine were inoculated with the Lactobacillus isolates and the E. coli model strain. After 8 and 24 h incubation, respectively, growth of the E. coli model strain was monitored by cultivation of the E. coli strain in antibiotic supplemented medium. By their superior inhibitory activity against the E. coli model strain, one L. agilis and one L. salivarius strain were selected and characterized for further application as probiotics in broiler chicken. Additionally, their antibiotic resistance patterns and resilience under gastric stress of isolates were also characterized. The results of this study demonstrate that the novel isolation procedure was able to efficiently and rapidly isolate and identify bacterial strains from a massive sample pool with inhibitory potential against specific types of bacteria (here E. coli). The introduction of the final ex vivo selection step additionally confirmed the inhibitory activity of the strains under conditions simulating the intestinal tract of the host. Furthermore, this method revealed a general potential for the isolation of antagonistic strains that active against other pathogenic bacteria with specific biomarker.

Lactobacillus reuteri Stimulates Intestinal Epithelial Proliferation and Induces Differentiation into Goblet Cells in Young Chickens

Probiotics, such as Lactobacillus, have been proven to be effective in maintaining intestinal homeostasis. The modulatory effect of Lactobacillus on intestinal epithelial development in early life is still unclear. In this study, Lactobacillus isolates with good probiotic abilities were screened and orally administered to detect their regulatory effect on intestinal development in chickens. L. reuteri 22 was isolated from chickens and chosen for subsequent chicken experiments due to its strong acid and bile salt resistance and ability to adhere to epithelial cells. The 3-day-old chickens were orally administrated with 10⁸ CFU L. reuteri 22 for consecutive 7 days. L. reuteri 22 increased Lgr5 mRNA expression (3.23 ± 0.40, P = 0.001) and activated the Wnt/β-catenin signaling pathway, with increasing expression of proliferating cell nuclear antigen (PCNA) (49.27 ± 9.81, P = 0.021) to support the proliferation of chicken intestinal epithelial cells. Moreover, L. reuteri 22 also inhibited the Notch signaling pathway to induce intestinal stem cell differentiation into goblet cells with increased mucin 2 (Muc-2) expression (1.72 ± 0.34, P = 0.047). L. reuteri 22 significantly enhanced lysozyme mRNA expression (2.32 ± 0.55, P = 0.019) to improve intestinal innate mucosal immunity. This study demonstrated that L. reuteri administration could regulate chicken intestinal epithelium development to ensure the function of the intestinal mucosal barrier, which is beneficial for newborn animals.

Comparative genomics of eight Lactobacillus buchneri strains isolated from food spoilage

Abstract

Background

Lactobacillus buchneri is a lactic acid bacterium frequently associated with food bioprocessing and fermentation and has been found to be either beneficial or detrimental to industrial food processes depending on the application. The ability to metabolize lactic acid into acetic acid and 1,2-propandiol makes L. buchneri invaluable to the ensiling process, however, this metabolic activity leads to spoilage in other applications, and is especially damaging to the cucumber fermentation industry. This study aims to augment our genomic understanding of L. buchneri in order to make better use of the species in a wide range of applicable industrial settings.

Results

Whole-genome sequencing (WGS) was performed on seven phenotypically diverse strains isolated from spoiled, fermented cucumber and the ATCC type strain for L. buchneri, ATCC 4005. Here, we present our findings from the comparison of eight newly-sequenced and assembled genomes against two publicly available closed reference genomes, L. buchneri CD034 and NRRL B-30929. Overall, we see ~ 50% of all coding sequences are conserved across these ten strains. When these coding sequences are clustered by functional description, the strains appear to be enriched in mobile genetic elements, namely transposons. All isolates harbor at least one CRISPR-Cas system, and many contain putative prophage regions, some of which are targeted by the host’s own DNA-encoded spacer sequences.

Conclusions

Our findings provide new insights into the genomics of L. buchneri through whole genome sequencing and subsequent characterization of genomic features, building a platform for future studies and identifying elements for potential strain manipulation or engineering.

In Vitro Evaluation of Probiotic Properties of Lactic Acid Bacteria Isolated from Some Traditionally Fermented Ethiopian Food Products

Probiotics are live microorganisms which when consumed in large number together with a food promote the health of the consumer. The aim of this study was to evaluate in vitro probiotic properties of lactic acid bacteria (LAB) isolated from traditional Ethiopian fermented Teff injera dough, Ergo, and Kocho products. A total of 90 LAB were isolated, of which 4 (4.44%) isolates showed 45.35–97.11% and 38.40–90.49% survival rates at pH values (2, 2.5, and 3) for 3 and 6 h, in that order. The four acid-tolerant isolates were found tolerant to 0.3% bile salt for 24 h with 91.37 to 97.22% rate of survival. The acid-and-bile salt-tolerant LAB isolates were found inhibiting some food-borne test pathogenic bacteria to varying degrees. All acid-and-bile-tolerant isolates displayed varying sensitivity to different antibiotics. The in vitro adherence to stainless steel plates of the 4 screened probiotic LAB isolates were ranged from 32.75 to 36.30% adhesion rate. The four efficient probiotic LAB isolates that belonged to Lactobacillus species were identified to the strain level using 16S rDNA gene sequence comparisons and, namely, were Lactobacillus plantarum strain CIP 103151, Lactobacillus paracasei subsp. tolerans strain NBRC 15906, Lactobacillus paracasei strain NBRC 15889, and Lactobacillus plantarum strain JCM 1149. The four Lactobacillus strains were found to be potentially useful to produce probiotic products.

Lactic Acid Bacteria from Kefir Increase Cytotoxicity of Natural Killer Cells to Tumor Cells

The Japanese fermented beverage, homemade kefir, contains six lactic acid bacteria: Lactococcus. lactis subsp. Lactis, Lactococcus. lactis subsp. Cremoris, Lactococcus. Lactis subsp. Lactis biovar diacetylactis, Lactobacillus plantarum, Leuconostoc meseuteroides subsp. Cremoris and Lactobacillus casei. In this study, we found that a mixture of the six lactic acid bacteria from kefir increased the cytotoxicity of human natural killer KHYG-1 cells to human chronic myelogenous leukemia K562 cells and colorectal tumor HCT116 cells. Furthermore, levels of mRNA expression and secretion of IFN-γ (interferon gamma) increased in KHYG-1 cells that had been treated with the six lactic acid bacteria mixture from kefir. The results suggest that the six lactic acid bacteria mixture from kefir has strong effects on natural immunity and tumor cell cytotoxicity.