In vitro testing of commercial and potential probiotic lactic acid bacteria

Wood hemicelluloses as protective materials for preserving the viability of probiotic Lacticaseibacillus rhamnosus GG during spray drying

Wood hemicelluloses from forest industry side-streams are promising economic and sustainable alternatives for encapsulating bioactive compounds. This study explores their suitability for probiotic encapsulation, specifically for maintaining cell viability and structure. The ability of galactoglucomannans (GGM) and glucuronoxylans (GX) to support the survival of Lacticaseibacillus rhamnosus GG (LGG) during spray drying at solid feed concentrations of 15 and 20 % and inlet air temperatures of 105 and 140 °C (outlet air temperature of 50 °C) was investigated and compared to the results obtained using maltodextrin (MD). Across all investigated conditions, LGG survival rates exceeded 85 % (>107 cfu/g) in GX and GGM microcapsule powders, which similar to that in MD microcapsules despite the differences in pH, particle size, and viscosity of their feed dispersions. The GX microcapsules demonstrated the highest process yield (50-58 %), followed by MD (39-51 %). All the microcapsule powders exhibited an amorphous structure consisting of spherical particles with an average diameter of 10 μm, sufficient for LGG accommodation. Atomic force microscopy analysis confirmed the encapsulation of LGG cells within microcapsules with intact rod-shaped chains post-spray drying. Overall, the spray-dried microencapsulation of probiotics using wood hemicelluloses maintains high probiotic viability and offers an eco-friendly, cost-effective alternative to traditional materials.

Akkermansia muciniphila: new insights into resistance to gastrointestinal stress, adhesion, and protein interaction with human mucins through optimised in vitro trials and bioinformatics tools

According to the FAO/WHO guidelines, selection of probiotics requires the assessment of survival under gastrointestinal stress and adhesion to human epithelial cells. These attributes were evaluated on Akkermansia muciniphila ATCC BAA-835 simulating the gastrointestinal transit (GIT) immediately followed by adhesion to human intestinal cell lines (CaCo2, HT-29, and HT-29-MTX) as an alternative approach to in vitro methods performed with fresh cells in each trial. The survival rate after GIT, as determined by plate counts and fluorescent probes, was significantly higher for A. muciniphila (about 8 Log CFU/mL) than for the probiotic Lacticaseibacillus rhamnosus GG ATCC 53103 (about 3 Log CFU/mL). The use of Live/Dead assay highlighted that A. muciniphila forms cell aggregates in the gastric phase as protective mechanism, explaining its high viability in the intestine. The rate of adhesion to human cell lines was always lower for strains tested after simulated GIT than for strains that did not undergo simulated GIT. Akkermansia muciniphila exhibited significantly higher adhesion than Lbs. rhamnosus GG, particularly to the mucus-secreting HT-29-MTX cells across a range of concentrations (2-8 Log CFU/mL). Finally, the bioinformatic analysis of A. muciniphila proteome confirmed the Amuc_1434 as a potential factor in binding to the human MUC2 protein.

The effects of a 6-week intervention with Limosilactobacillus reuteri ATCC PTA 6475 alone and in combination with L. reuteri DSM 17938 on gut barrier function, immune markers, and symptoms in patients with IBS-D-An exploratory RCT

BACKGROUND

An increased intestinal permeability is a common feature in patients with diarrhoea-predominant irritable bowel syndrome (IBS-D). Probiotics have shown to improve IBS symptoms and might also affect intestinal barrier function.

AIM

The aim of this study was to investigate the effects of a 6-week intervention with Limosilactobacillus reuteri ATCC PTA 6475 alone (single strain) or in combination with Limosilactobacillus reuteri DSM 17938 (dual strain) on gut barrier function, immune markers, and symptoms in IBS-D patients (ClinicalTrials.gov registration number: NCT03986476).

METHODS

65 IBS-D patients were randomised into three groups (placebo, single strain, dual strain). Small and large intestinal permeability were assessed using a multi-sugar urinary recovery test. Blood, saliva, faecal samples, and several symptom scales were collected before, and after three and six weeks of intervention.

RESULTS

Small and large intestinal permeability as well as other markers of gut barrier function were not significantly affected by the probiotic interventions. Serum IL-6 levels showed a tendency to be reduced in the single strain group (descriptive p = 0.052). In addition, high-sensitivity C-reactive protein was significantly reduced in the dual strain group (p = 0.041). The participants in both treatment groups reported less gastrointestinal symptoms after three weeks, but this reached significance only in the dual strain group (total score: p = 0.032, pain subscore: p = 0.028). After six weeks, none of the assessed symptoms were significantly different from the placebo.

CONCLUSION

The probiotic compounds investigated in this study did not seem to affect IBS-D patients' gut barrier function, but showed potential anti-inflammatory and symptom-improving properties, which need to be confirmed in larger study cohorts.

Isolation, characterization of Weissella confusa and Lactococcus lactis from different milk sources and determination of probiotic features

This study aimed to investigate the probiotic properties of Lactic Acid Bacteria (LAB) isolates derived from various milk sources. These isolates identified based on their morphological characteristics and 16S rRNA gene sequencing. Four strains of Lactococcus lactis and two strains of Weissella confusa were identified with over 96% 16S rRNA gene similarity according to the NCBI-BLAST results. The survival of the isolates was determined in low pH, pepsin, bile salts, and pancreatin, and their adhesion ability was assessed by in vitro cell adhesion assay, hydrophobicity, auto- and co-aggregation, and safety criteria were determined by hemolytic, gelatinase activities, and DNAse production ability tests. The results showed that the LAB isolates had different levels of resistance to various stress factors. L. lactis subsp. cremoris MH31 showed the highest resistance to bile salt, while the highest pH resistance was observed in L. lactis MH31 at pH 3.0. All the isolates survived in pepsin exposure at pH 3.0 for 3 h. The auto-aggregation test results showed that all strains exhibited auto-aggregation ranging from 84.9 to 91.4%. Co-aggregation percentage ranged from 19 - 54% and 17 - 57% against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213, respectively. The hydrophobicity capacity of the LAB isolated ranged from 35-61%. These isolates showed different adhesion abilities to Caco-2 cells (81.5% to 92.6%). None of the isolates exhibited DNase, gelatinase and hemolytic activity (γ-hemolysis). All results indicate that these LAB strains have the potential to be used as probiotics.

Determination of the Viability of Lactic Acid Bacteria by Dynamic In Vitro Gastrointestinal Model in Household and Industrial-Type Kefir Samples

This study presents results based on differences in the antioxidant activity and lactic acid bacteria counts in different parts of the digestive tract following simulated gastrointestinal digestion of kefir samples. Statistically significant differences were observed in Lactobacillus counts in different kefir types including industrial (IK), starter culture (SCK), and kefir grains (KG). These differences were observed between the initial and second min in the mouth region (T = 3.968; p < 0.05); and between the initial, 60th, and 120th min in the stomach region (R = 11.146; p < 0.05). Additionally, a statistically significant difference was noted in the initial Lactobacillus levels among the IK, SCK, and KG in the stomach region (H = 7.205; p < 0.05). Also, significant differences were identified between the Lactococcus counts of IK across 0, 60, and 120 min in the stomach region (R = 10.236; p < 0.05). Notably, a statistically significant difference was noted in the Lactococcus levels in the KG between the initial and second min in the mouth region (T = 3.101; p < 0.05) and between 0, 60, and 120 min in the stomach region (R = 25.771; p < 0.001). These findings highlight the differences between the physicochemical characteristics of different kefir types. A decrease in lactic acid bacteria counts in kefir samples was observed throughout the dynamic in vitro gastrointestinal tract to reveal the significance of the digestive process when determining probiotic product capacity.

Prebiotics and Probiotics: Therapeutic Tools for Nonalcoholic Fatty Liver Disease

Alterations in the gut-liver axis and changes in the gut microbiome are among the risk factors for the pathogenesis of non-alcoholic fatty liver disease (NAFLD). These patients show increased bacterial overgrowth in the small intestine and impaired intestinal permeability. Therefore, therapeutic options such as probiotics or prebiotics have been investigated to modulate intestinal microbiota composition to improve NAFLD. Most in vivo and in vitro probiotic studies have focused on reducing hepatic fat accumulation. The beneficial effects of probiotics on NAFLD have been demonstrated in animal models, and the most widely used microorganisms are those of the Lactobacillus and Bifidobacterium genera. In animal models, probiotics help restore the intestinal microbiota and improve the integrity of the intestinal barrier. This narrative review summarizes published evidence and the likely benefits of probiotics and prebiotics as a therapeutic option for patients with NAFLD.

Diversity of the Microbiota of Traditional Izmir Tulum and Izmir Brined Tulum Cheeses and Selection of Potential Probiotics

High-throughput DNA sequencing (HTS) was used to study the microbial diversity of commercial traditional Izmir Tulum (IT) and Izmir Brined Tulum (IBT) cheeses from Izmir, Türkiye. Simultaneously, cultivation-dependent methods were used to isolate, identify and characterize bacterial strains displaying probiotic potential. At the phylum level, Firmicutes dominated the microbiota of both cheese types comprising >98% of the population. Thirty genera were observed, with Streptococcus being the most abundant genus and with Streptococcus thermophilus and S. infantarius subsp. infantarius being the most abundant species. Genera, including Bifidobacterium and Chryseobacterium, not previously associated with IT and IBT, were detected. IT cheeses displayed higher operational taxonomic units (OTUs; Richness) and diversity index (Simpson) than IBT cheeses; however, the difference between the diversity of the microbiota of IT and IBT cheese samples was not significant. Three Lacticaseibacillus paracasei strains isolated from IBT cheeses exhibited probiotic characteristics, which included capacity to survive under in vitro simulated gastrointestinal conditions, resistance to bile salts and potential to adhere to HT-29 human intestinal cells. These findings demonstrate that Tulum cheeses harbor bacterial genera not previously reported in this cheese and that some strains display probiotic characteristics.

Probiotic characterization and comparison of broiler-derived lactobacillus strains based on technique for order preference by similarity to ideal solution analysis

A total of 10 lactobacillus strains were isolated from broiler chickens and their probiotic properties including tolerance to gastrointestinal fluids and heat treatment, antimicrobial activity, adhesion capacity to intestinal cells, surface hydrophobicity, autoaggregation, antioxidative activity, and immunomodulatory effects on chicken macrophages were evaluated. The Limosilactobacillus reuteri (LR) was the most frequently isolated species, followed by Lactobacillus johnsonii (LJ) and Ligilactobacillus salivarius (LS). All isolates showed good resistance to simulated gastrointestinal conditions and antimicrobial activity against 4 indicator strains including Escherichia coli, Salmonella typhimurium, Klebsiella pneumoniae, and Proteus mirabilis LR 21 exhibited excellent performances on autoaggregation, hydrophobicity and adhesion capacity to Caco-2 intestinal cells. In the meantime, this strain also possessed considerable tolerance to heat treatment, which indicated great potential to be used in the feed industry. However, LJ 20 strain had the highest free radical scavenging activity compared with the other strains. Furthermore, qRT-PCR results revealed that all isolated strains significantly increased the transcriptional levels of proinflammatory genes and tended to induce the M1-type polarization on HD11 macrophages. Particularly, the technique for order preference by similarity to ideal solution (TOPSIS) was adopted in our study to compare and select the most promising probiotic candidate based on in vitro evaluation tests.

Inhibition of Listeria monocytogenes Growth, Adherence and Invasion in Caco-2 Cells by Potential Probiotic Lactic Acid Bacteria Isolated from Fecal Samples of Healthy Neonates

Lactic acid bacteria (LAB) isolated from healthy humans may prove an effective tool against pathogen growth, adherence and invasion in intestinal epithelial cells. This study aimed to evaluate the antilisterial properties of LAB isolated from fecal samples of healthy neonates. Forty-five LAB strains were tested for their antimicrobial activity against ten Listeria monocytogenes strains with spot-on-lawn and agar-well diffusion assays, and ten lactobacilli strains were further assessed for their inhibitory effect against adherence and invasion of Caco-2 cells by L. monocytogenes EGDe. Inhibition was estimated in competition, exclusion or displacement assays, where lactobacilli and L. monocytogenes were added to Caco-2 monolayers simultaneously or 1 h apart from each other. Inhibition of L. monocytogenes growth was only displayed with the spot-on-lawn assay; cell-free supernatants of lactobacilli were not effective against the pathogen. Lactobacillus (L.) paragasseri LDD-C1 and L. crispatus LCR-A21 were able to adhere to Caco-2 cells at significantly higher levels than the reference strain L. rhamnosus GG. The adherence of L. monocytogenes to Caco-2 cells was reduced by 20.8% to 62.1% and invasion by 33.5% to 63.1% during competition, which was more effective compared to the exclusion and displacement assays. These findings demonstrate that lactobacilli isolated from neonatal feces could be considered a good candidate against L. monocytogenes.

Inflammatory Bowel Disease-Associated Gut Commensals Degrade Components of the Extracellular Matrix

Extracellular matrix (ECM) remodeling has emerged as a key feature of inflammatory bowel disease (IBD), and ECM fragments have been proposed as markers of clinical disease severity. Recent studies report increased protease activity in the gut microbiota of IBD patients. Nonetheless, the relationship between gut microbiota and ECM remodeling has remained unexplored. We hypothesized that members of the human gut microbiome could degrade the host ECM and that bacteria-driven remodeling, in turn, could enhance colonic inflammation. Through a variety of in vitro assays, we first confirmed that multiple bacterial species found in the human gut are capable of degrading specific ECM components. Clinical stool samples obtained from ulcerative colitis patients also exhibited higher levels of proteolytic activity in vitro, compared to those of their healthy counterparts. Furthermore, culture supernatants from bacteria species that are capable of degrading human ECM accelerated inflammation in dextran sodium sulfate (DSS)-induced colitis. Finally, we identified several of the bacterial proteases and carbohydrate degrading enzymes (CAZymes) that are potentially responsible for ECM degradation in vitro. Some of these protease families and CAZymes were also found in increased abundance in a metagenomic cohort of IBD. These results demonstrate that some commensal bacteria in the gut are indeed capable of degrading components of human ECM in vitro and suggest that this proteolytic activity may be involved in the progression of IBD. A better understanding of the relationship between nonpathogenic gut microbes, host ECM, and inflammation could be crucial to elucidating some of the mechanisms underlying host-bacteria interactions in IBD and beyond. IMPORTANCE Healthy gut epithelial cells form a barrier that keeps bacteria and other substances from entering the blood or tissues of the body. Those cells sit on scaffolding that maintains the structure of the gut and informs our immune system about the integrity of this barrier. In patients with inflammatory bowel disease (IBD), breaks are formed in this cellular barrier, and bacteria gain access to the underlying tissue and scaffolding. In our study, we discovered that bacteria that normally reside in the gut can modify and disassemble the underlying scaffolding. Additionally, we discovered that changes to this scaffolding affect the onset of IBD in mouse models of colitis as well as the abilities of these mice to recover. We propose that this new information will reveal how breaks in the gut wall lead to IBD and will open up new avenues by which to treat patients with IBD.

In vitro assessment of probiotic attributes for strains contained in commercial formulations

Although probiotics are often indiscriminately prescribed, they are not equal and their effects on the host may profoundly differ. In vitro determination of the attributes of probiotics should be a primary concern and be performed even before clinical studies are designed. In fact, knowledge on the biological properties a microbe possesses is crucial for selecting the most suitable bacteriotherapy for each individual. Herein, nine strains (Bacillus clausii NR, OC, SIN, T, Bacillus coagulans ATCC 7050, Bifidobacterium breve DSM 16604, Limosilactobacillus reuteri DSM 17938, Lacticaseibacillus rhamnosus ATCC 53103, and Saccharomyces boulardii CNCM I-745) declared to be contained in six commercial formulations were tested for their ability to tolerate simulated intestinal conditions, adhere to mucins, and produce β-galactosidase, antioxidant enzymes, riboflavin, and D-lactate. With the exception of B. breve, all microbes survived in simulated intestinal fluid. L. rhamnosus was unable to adhere to mucins and differences in mucin adhesion were evidenced for L. reuteri and S. boulardii depending on oxygen levels. All microorganisms produced antioxidant enzymes, but only B. clausii, B. coagulans, B. breve, and L. reuteri synthesize β-galactosidase. Riboflavin secretion was observed for Bacillus species and L. rhamnosus, while D-lactate production was restricted to L. reuteri and L. rhamnosus. Our findings indicate that the analyzed strains possess different in vitro biological properties, thus highlighting the usefulness of in vitro tests as prelude for clinical research.

Functional genomics of the lactic acid bacterium Limosilactobacillus fermentum LAB-1: metabolic, probiotic and biotechnological perspectives

A genome-based systematic analysis was conducted to characterize the metabolic, probiotic, fitness, and safety properties of Limosilactobacillus fermentum LAB-1, a lactic acid bacterium demonstrating strong antimicrobial effects against clinical pathogens. Gene functional characterization revealed a large number of genes for carbohydrate metabolism and a heterofermentative system for carbon dissimilation. Genes for intact pyruvate oxidation, pentose phosphate, and PRPP biosynthetic pathways were identified. Substantial carbohydrate-active enzymes and transporters were also predicted. Metabolic reconstruction revealed complete sets of enzymes for arginine, lysine, methionine, threonine, proline, and ornithine biosynthesis. The bacterium harbors a diverse range of peptidases, and a large variety of peptide and amino acid uptake systems. It encodes restriction-modification and CRISPR-Cas systems for protection against phage infections and carries a wide spectrum of stress proteins for adaptation in the gut and industrial conditions. Genes related to the biosynthesis of B-group and K vitamins were identified allowing its application for novel bio-enriched food production. Other beneficial traits of probiotic and industrial importance such as production of flavor compounds, exopolysaccharide, acetoin, and butanediol were identified. Three antimicrobial peptides were predicted which showed >98% sequence-identity to experimentally validated bacteriocins. Negative traits such as transmissible antibiotic resistance, pathogenicity or virulence appeared to be absent suggesting the strain to be considered safe. The genome analysis will allow precisely targeted laboratory research and full exploitation of the probiotic potentials towards functional-food, biotechnology and health-related applications.

Sheep Milk Symbiotic Ice Cream: Effect of Inulin and Apple Fiber on the Survival of Five Probiotic Bacterial Strains during Simulated In Vitro Digestion Conditions

We conducted a study to determine the survival of bacterial cells under in vitro digestion. For this purpose, ice cream mixes were prepared: control, with 4% inulin, 2.5% inulin and 1.5% apple fiber and 4% apple fiber. Each inoculum (pH = 4.60 ± 0.05), containing 9 log cfu g^-1 bacteria, at 5% (w/w) was added to the ice cream mixes (Lacticaseibacilluscasei 431, Lactobacillus acidophilus LA-5, Lacticaseibacillus paracasei L-26, Lacticaseibacillusrhamnosus, Bifidobacterium animalis ssp. lactis BB-12) and fermentation was carried out to pH 4.60 ± 0.05. The in vitro digestion method simulated the stages of digestion that occur in the mouth, stomach and small intestine under optimal controlled conditions (pH value, time and temperature). At each stage of digestion, the survival rate of probiotic bacteria was determined using the plate-deep method. As expected, in the oral stage, there was no significant reduction in the viability of the probiotic bacteria in any ice cream group compared to their content before digestion. In the stomach stage, Bifidobacterium animalis ssp. lactis BB-12 strain had the highest viable counts (8.48 log cfu g^-1) among the control samples. Furthermore, a 4% addition of inulin to ice cream with Bifidobacterium BB-12 increased gastric juice tolerance and limited strain reduction by only 16.7% compared to the number of bacterial cells before digestion. Regarding ice cream samples with Bifidobacterium BB-12, replacing part of the inulin with apple fiber resulted in increased survival at the stomach stage and a low reduction in the bacterial population of only 15.6% compared to samples before digestion. At the stomach stage, the positive effect of the addition of inulin and apple fiber was also demonstrated for ice cream samples with Lacticaseibacilluscasei 431 (9.47 log cfu g^-1), Lactobacillus acidophilus LA-5 (8.06 log cfu g^-1) and Lacticaseibacillus paracasei L-26 (5.79 log cfu g^-1). This study showed the highest sensitivity to simulated gastric stress for ice cream samples with Lacticaseibacillusrhamnosus (4.54 log cfu g^-1). Our study confirmed that the 4% addition of inulin to ice cream increases the survival rate of L. casei and Bifidobacterium BB-12 in simulated intestinal juice with bile by 0.87 and 2.26 log cfu g^-1, respectively. The highest viable count in the small intestine stage was observed in ice cream with L. acidophilus. The addition of inulin increased the survival of L. rhamnosus by 10.8% and Bifidobacterium BB-12 by about 22% under conditions of simulated in vitro digestion compared to their control samples. The survival rates of L. casei and L. paracasei were also highly affected by the 4% addition of apple fiber, where the increase under gastrointestinal passage conditions was determined to range from 7.86-11.26% compared to their control counterparts. In comparison, the lowest survival rate was found in the control ice cream with L. rhamnosus (47.40%). In our study at the intestinal stage, only five ice cream groups: a sample with 4% inulin and L. acidophilus, a control sample with Bifidobacterium BB12, a sample with 2.5% inulin and 1.5% apple fiber with Bifidobacterium BB12, a control sample with L. rhamnosus, a sample with 4% fiber and L. rhamnosus reported bacterial cell counts below 6 log cfu g^-1 but higher than 5 log cfu g^-1. However, in the remaining ice cream groups, viable counts of bacterial cells ranged from 6.11 to 8.88 log cfu g^-1, ensuring a therapeutic effect. Studies have clearly indicated that sheep milk ice cream could provide a suitable matrix for the delivery of probiotics and prebiotics and contribute to intestinal homeostasis. The obtained results have an applicative character and may play an essential role in developing new functional sheep milk ice cream.

Preliminary evaluation of probiotic properties and safety profile of Lactiplantibacillus plantarum isolated from spontaneously fermented milk, Amabere amaruranu

The aim of this study was to assess the probiotic potential and safety profile of a Lactiplantibacillus plantarum EGER41 strain isolated from Kenyan spontaneously fermented milk, Amabere amaruranu. The L. plantarum EGER41 isolate was tested for temperature sensitivity (at 15 °C, 30 °C, 37 °C, and 45 °C), pH tolerance (at 2.0, 2.5, 3.0, 3.5, and 6.5 as control), and 0.4% phenol tolerance to observe its survival in the gastrointestinal tract of humans. For safety evaluation of the isolate, antagonistic activity was tested against pathogenic strains of Staphylococcus aureus, Escherichia coli, Salmonella enterica serovar Typhi, and Candida albicans, while antibiotic susceptibility pattern was examined using nalidixic acid, ampicillin, azithromycin, ciprofloxacin, tetracycline, gentamicin, and chloramphenicol antibiotic discs and haemolytic activity was done using lamb blood agar. The L. plantarum isolate had an optimal growth at 37 °C, it also demonstrated low pH tolerance (2.0–3.5). It was able to maintain its viability (∼100%) after exposure to 0.4% phenol. The selected isolate showed inhibition (antagonistic activity) against the pathogens with S. typhi having the largest (ZDI = 31.0 ± 1.73 mm) zone of diameter inhibition (ZDI) and Candida albicans having the least (ZDI = 18.0 ± 0.76 mm). L. plantarum isolate was sensitive to Azithromycin, tetracycline and chloramphenicol and was intermediately sensitive to gentamycin, while it was resistant to nalidixic acid, ampicillin, and ciprofloxacin. The isolate also exhibited γ-haemolytic activity hence safe for use as a starter culture and was identified as a Lactiplantibacillus plantarum EGER 41 strain based on 16S rRNA gene sequencing. The selected isolate can potentially be used as a starter culture and a probiotic since it had excellent probiotic properties.

Optimizing Conditions in the Acid Tolerance Test for Potential Probiotics Using Response Surface Methodology

Acid tolerance is an important feature of probiotic development. It is one of the factors underlying the beneficial effects of probiotics in the intestine. However, the methods used by different researchers to test acid tolerance vary, causing confusion in the interpretation of the results. Therefore, in this study, we determine the optimal conditions for the acid tolerance test using response surface methodology. The factors of pH (2.5 to 3.5), exposure time (1 to 2 h), and pepsin (presence or absence) were used as independent variables, and the survival rates of seven strains (Lacticaseibacillus casei KACC 12413, Lactiplantibacillus plantarum KACC 15357, Limosilactobacillus fermentum KACC 11441, Lactiplantibacillus plantarum WCFS1, Lacticaseibacillus rhamnosus GG, Lactiplantibacillus plantarum KCTC 21024, and Lactiplantibacillus plantarum WiKim 0112) known to have probiotic properties were used as dependent variables. The results of the analysis of variance (ANOVA) indicated that the pH value and exposure time in acidic environments significantly affected the acid tolerance test model, and their interaction also had an effect (P < 0.05). Using the ANOVA results, the condition of the acid tolerance test was optimized with a target of an 85% survival rate for each strain. The optimized conditions of the acid tolerance test were as follows: pH 2.92, exposure time of 1.73 h, and presence of pepsin and pH 3, exposure time of 1.98 h, and absence of pepsin. These results can optimize strain selection with rigorous acid tolerance without confusion by unifying the conditions for the acid tolerance test. IMPORTANCE The acid tolerance test, which is the first step in selecting probiotics, is not standardized and can often cause confusion in the interpretation of results. Thus, in the present study, we optimized the conditions for the acid tolerance test using response surface methodology. These optimized conditions can be used to screen for strains with acid tolerance.

Bacteriocinogenic probiotic bacteria isolated from an aquatic environment inhibit the growth of food and fish pathogens

The conditions of aquatic environments have a great influence on the microbiota of several animals, many of which are a potential source of microorganisms of biotechnological interest. In this study, bacterial strains isolated from aquatic environments were bioprospected to determine their probiotic profile and antimicrobial effect against fish and food pathogens. Two isolates, identified via 16S rRNA sequencing as Lactococcus lactis (L1 and L2) and one as Enterococcus faecium 135 (EF), produced a bacteriocin-like antimicrobial substance (BLIS), active against Listeria monocytogenes, Salmonella Choleraesuis and Salmonella Typhimurium. Antimicrobial activity of BLIS was reduced when exposed to high temperatures and proteolytic enzymes (trypsin, pepsin, papain and pancreatin). All strains were sensitive to 7 types of antibiotics (vancomycin, clindamycin, streptomycin, gentamicin, chloramphenicol, rifampicin and ampicillin), exhibited a high rate of adherence to Caco-2 cells and expressed no hemolysin and gelatinase virulence factors. EF showed some resistance at pH 2.5 and 3.0, and L2/EF showed higher resistance to the action of bile salts. Finally, the presence of bacteriocin genes encoding for proteins, including Nisin (L1 and L2), Enterocin A, B, P, and Mundticin KS (EF) was detected. The molecular and physiological evidence suggests that the bacterial isolates in this study could be used as natural antimicrobial agents and may be considered safe for probiotic application.

Determination of Antiviral Mechanism of Centenarian Gut-Derived Limosilactobacillus fermentum Against Norovirus

Although noroviruses are the causative agents of most non-bacterial foodborne disease outbreaks, effective antivirals are currently unavailable. Certain probiotic strains have been reported as active antivirals for norovirus infections, but their mechanisms have not been fully elucidated. Herein, we examined the antiviral potential of 122 lactic acid bacteria isolates against murine norovirus (MNV), a human norovirus surrogate. A centenarian gut-derived strain, Limosilactobacillus fermentum PV22, exhibited the strongest MNV antagonism and reduced the viral titer by 2.23 ± 0.38 (log-value) in 5 min with stable activity at 25°C (P < 0.01). Genome mining revealed that its antiviral activity can be attributed to the synthesis of γ-aminobutyric acid, and this finding was experimentally verified. Furthermore, we demonstrated the safety of the isolate and its high intestinal colonization ability. In conclusion, we discovered a centenarian gut-derived L. fermentum strain with strong anti-norovirus activity and identified its antiviral metabolite. Our results will offer new solutions for the prevention and treatment of food-related norovirus infections.

The Combination of In Vitro Assessment of Stress Tolerance Ability, Autoaggregation, and Vitamin B-Producing Ability for New Probiotic Strain Introduction

The health benefits of probiotics are beyond doubt. The positive effects of lactobacilli and bifidobacteria on the function of many body systems have been repeatedly proven by various studies. To completely realize the potential of probiotic microorganisms, the strains should be tested by the greatest combination of characteristics that contribute to the wellness of the host. In this work, for the first time, a combined assessment of the probiotic properties and vitamin B-producing potential of various species and strains of bifidobacteria and lactobacilli was carried out. The presence of an additional advantage, such as vitamin-producing ability, can prevent vitamin deficiency both at the level of the consumption of fermented foods, when the enrichment will occur naturally on the spot, and during colonization by these intestinal strains, when synthesis will occur in vivo. To select potential probiotics, the stress tolerance ability of 16 lactic acid bacteria and bifidobacteria strains to low pH values, bile, and proteolytic enzymes, as well as their ability to autoaggregate, were studied under conditions of modeling the gastrointestinal tract in vitro. The ability of the strains to extracellularly accumulate water-soluble B vitamins was evaluated by capillary electrophoresis. Among the tested strains of bifidobacteria, B. adolescentis VKPM AC-1662 is of interest; it was characterized by the greatest stress tolerance ability and the ability to autoaggregate, in addition to the extracellular synthesis of riboflavin and pyridoxine. Among lactic acid bacteria, L. sakei VKPM B-8936 demonstrated the greatest tolerance to low pH, L. plantarum VKPM B–11007 to duodenal conditions, L. acidophilus VKPM B-2213 to pepsin, and L. salivarius VKPM B–2214 to pancreatin. The highest percentage of autoaggregation was observed in L. salivarius VKPM B-2214, which also accumulated the largest amount of pantothenic acid, but it was sensitive to stress conditions. The obtained results could be used to create new products enriched with probiotics and B vitamins.

First characterization of the probiotic potential of lactic acid bacteria isolated from Costa Rican pineapple silages

Background

Agro-industrial waste from tropical environments could be an important source of lactic acid bacteria (LAB) with probiotic potential.

Methods

Twelve LAB isolates were isolated from pineapple silages. The species identification was carried out considering 16S rRNA and pheS genes. Experiments to evaluate the probiotic potential of the isolates included survival under simulated gastrointestinal environment, in vitro antagonistic activity (against Salmonella spp. and Listeria monocytogenes), auto-aggregation assays, antibiotic susceptibility, presence of plasmids, adhesiveness to epithelial cells, and antagonistic activity against Salmonella in HeLa cells.

Results

Lacticaseibacillus paracasei, Lentilactobacillus parafarraginis, Limosilactobacillus fermentum, and Weissella ghanensis were identified. Survival of one of the isolates was 90% or higher after exposure to acidic conditions (pH: 2), six isolates showed at least 61% survival after exposure to bile salts. The three most promising isolates, based on survivability tests, showed a strong antagonistic effect against Salmonella. However, only L. paracasei_6714 showed a strong Listeria inhibition pattern; this isolate showed a good auto-aggregation ability, was resistant to some of the tested antibiotics but was not found to harbor plasmids; it also showed a high capacity for adhesion to epithelial cells and prevented the invasion of Salmonella in HeLa cells. After further in vivo evaluations, L. paracasei_6714 may be considered a probiotic candidate for food industry applications and may have promising performance in acidic products due to its origin.

Lactiplantibacillus plantarum 299v (LP299V®): three decades of research

This review aims to provide a comprehensive overview of the in vitro, animal, and clinical studies with the bacterial strain Lactiplantibacillus plantarum 299v (L. plantarum 299v; formerly named Lactobacillus plantarum 299v) published up until June 30, 2020. L. plantarum 299v is the most documented L. plantarum strain in the world, described in over 170 scientific publications out of which more than 60 are human clinical studies. The genome sequence of L. plantarum 299v has been determined and is available in the public domain (GenBank Accession number: NZ_LEAV01000004). The probiotic strain L. plantarum 299v was isolated from healthy human intestinal mucosa three decades ago by scientists at Lund University, Sweden. Thirty years later, a wealth of data coming from in vitro, animal, and clinical studies exist, showing benefits primarily for gastrointestinal health, such as reduced flatulence and abdominal pain in patients with irritable bowel syndrome (IBS). Moreover, several clinical studies have shown positive effects of L. plantarum 299v on iron absorption and more recently also on iron status. L. plantarum 299v is safe for human consumption and does not confer antibiotic resistance. It survives the harsh conditions of the human gastrointestinal tract, adheres to mannose residues on the intestinal epithelial cells and has in some cases been re-isolated more than ten days after administration ceased. Besides studying health benefits, research groups around the globe have investigated L. plantarum 299v in a range of applications and processes. L. plantarum 299v is used in many different food applications as well as in various dietary supplements. In a freeze-dried format, L. plantarum 299v is robust and stable at room temperature, enabling long shelf-lives of consumer healthcare products such as capsules, tablets, or powder sachets. The strain is patent protected for a wide range of indications and applications worldwide as well as trademarked as LP299V^®.

Lactobacillus plantarum and Lactobacillus reuteri as Functional Feed Additives to Prevent Diarrhoea in Weaned Piglets

Simple Summary

Antimicrobial resistance is an increasing global concern. Effective alternatives that could replace and reduce antimicrobial treatments in farming have therefore become crucial for animal, human and environmental health. In swine farming, weaning is a stressful phase where piglets can develop multifactorial enteric disorders that require antibiotic treatments. Functional nutrition could thus represent a valuable alternative to reduce and tackle antibiotic resistance. This study assesses the effects of Lactobacillus plantarum and Lactobacillus reuteri on in-feed supplementation in weaned piglets. After weaning, piglets were allotted to four experimental groups fed a basal diet (CTRL) and a basal diet supplemented with 2 × 10⁸ CFU/g of L. plantarum (PLA), L. reuteri and a combination of the two strains (P+R) for 28 days. Zootechnical performance and diarrhoea occurrence were recorded. Microbiological and serum metabolism analyses of faeces and blood samples were performed. Supplemented groups with lactobacilli showed a lower occurrence of diarrhoea and improved faecal consistency compared to the control. The PLA group registered the lowest diarrhoea frequency during the 28-day experimental period. The results suggest that dietary administration of L. plantarum and L. reuteri could prevent the occurrence of diarrhoea in weaned piglets.

Abstract

The effects of Lactobacillus plantarum and Lactobacillus reuteri and their combination were assessed in weaned piglets. Three hundred and fifty weaned piglets (Landrace × Large White), balanced in terms of weight and sex, were randomly allotted to four experimental groups (25 pens, 14 piglets/pen). Piglets were fed a basal control diet (CTRL, six pens) and a treatment diet supplemented with 2 × 10⁸ CFU/g of L. plantarum (PLA, 6 pens), 2 × 10⁸ CFU/g L. reuteri (REU, six pens) and the combination of both bacterial strains (1 × 10⁸ CFU/g of L. plantarum combined with 1 × 10⁸ CFU/g of L. reuteri, P+R, 7 pens) for 28 days. Body weight and feed intake were recorded weekly. Diarrhoea occurrence was assessed weekly by the faecal score (0–3; considering diarrhoea ≥ 2). At 0 and 28 days, faecal samples were obtained from four piglets per pen for microbiological analyses and serum samples were collected from two piglets per pen for serum metabolic profiling. Treatments significantly reduced diarrhoea occurrence and decreased the average faecal score (0.94 ± 0.08 CTRL, 0.31 ± 0.08 PLA, 0.45 ± 0.08 REU, 0.27 ± 0.08 P+R; p < 0.05). The PLA group registered the lowest number of diarrhoea cases compared to other groups (20 cases CTRL, 5 cases PLA, 8 cases REU, 10 cases P+R; p < 0.01). After 28 days, the globulin serum level increased in PLA compared to the other groups (24.91 ± 1.09 g/L CTRL, 28.89 ± 1.03 g/L PLA, 25.91 ± 1.03 g/L REU, 25.31 ± 1.03 g/L P+R; p < 0.05). L. plantarum and L. reuteri could thus be considered as interesting functional additives to prevent diarrhoea occurrence in weaned piglets.

In Vitro Screening of Chicken-Derived Lactobacillus Strains that Effectively Inhibit Salmonella Colonization and Adhesion

Inhibition of Salmonella by Lactobacillus has been a popular research topic for decades; however, the inhibition potential of chicken-derived Salmonella by chicken-derived Lactobacillus has not yet been studied. In this study, 89 strains of Lactobacillus from chicken intestines were isolated by national standard method, Gram staining, physiological, and biochemical experiments and molecular sequencing; The inhibition characteristics of 89 strains of chicken derived Lactobacillus against 10 strains Salmonella (S. Enteritidis SE05, SC31, SC21, SC72 SC74, SC79, SC83, SC87; S. bongori SE47; S. Typhimurium, SC85) were detected by agar inhibition zone, The results showed that the inhibition zone of 24 strains of chicken derived Lactobacillus was more than 10 mm, which indicated that the isolated chicken derived Lactobacillus could effectively inhibit the growth of Salmonella; The drug resistance and bile salt tolerance of these 24 strains were analyzed, The results showed that the standard strains LG and L76 were not resistant, and the other 22 Lactobacillus strains showed different degrees of resistance. The strains LAB24, LAB26, LAB53, LAB69, and L76 showed good tolerance at the concentration of 3 g/L bile salt; Caco-2 cell experiment and flow cytometry were used to analyze the inhibitory effect of chicken derived Lactobacillus on the adhesion of Salmonella to Caco-2 cells, The results showed that 16 probiotics could effectively inhibit the adhesion of Salmonella to Caco-2 cells. Twelve probiotics were identified by molecular biology. The results showed that L76 was Enterococcus faecalis, and the other 11 strains were Lactobacillus.

Development of a semi-dynamic in vitro model and its testing using probiotic Bacillus coagulans GBI-30, 6086 in orange juice and yogurt

A dynamic system mimicking the gastrointestinal tract (GIT) conditions (fluids, pH, temperature, and residence time) was used to evaluate the behavior of Bacillus coagulans GBI-30, 6086 (BC) incorporated in yogurt and orange juice. BC counts were monitored in samples collected before the in vitro digestion, after initial contact with gastric fluids (30 min), static (1 h 15 min) and dynamic (2 h) stages in the gastric compartment, static (3 h) and dynamic (4 h) stages in the duodenal compartment, static (5 h) and dynamic (6 h) stages in the jejunal compartment, and after digestion. BC presented high survival in juice and yogurt over the digestion stages. The number of decimal reductions (γ) of BC caused by exposure to simulated GIT conditions was ≥0.89 in orange juice and ≥1.17 in yogurt. No differences (p ≥ 0.05) were observed on the survival of BC among the samples collected over the digestion in juice or yogurt, or between these matrices. After the in vitro digestion, BC counts were ≥7 log CFU/mL or g. Results show the great survival of BC under GIT conditions and suggest both, juice and yogurt as appropriate carries for delivering this probiotic to the diet. The semi-dynamic in vitro system was easily built and to operate, comprising an intermediate approach to assess the resistance of probiotic or potentially probiotic strains under simulated gut conditions.

Use of Autochthonous Lactiplantibacillus plantarum Strains to Produce Fermented Fish Products

The present research was aimed to the optimization of the production of a fish fermented salami-like product using autochthonous Lactiplantibacillus plantarum starters. The activity was performed through two phases: (1) Optimization of fermented fish product composition by using a 2^k-p Fractional Factorial Design: the variables tested were nitrites (0–150 ppm), salt (2.5–7.5%), sucrose (0–4%), white pepper (0–0.10%), and fermentation temperature (10–30°C); (2) Product realization and evaluation of its microbiological profile [aerobic microbiota (APC), Pseudomonadaceae (PSE), Enterobacteriaceae (E), and lactic acid bacteria (LAB) populations], chemico-physical parameters (pH and a_w), and sensorial quality (odor, texture, color, and overall acceptability) during its storage at 4°C for 21 days. In the first step, the fish pulp was mixed with the appropriate amounts of ingredients, according to the experimental design; each batch was individually inoculated with the studied starter (L. plantarum 11, L. plantarum 69, and L. plantarum DSM1055) at 10⁷ cfu/g and incubated at 10, 20, or 30°C for 7 days. The lowest fermentation time (time to reach pH 4.4) was obtained with 4% sucrose, 100 ppm nitrite and a process temperature of 30°C. In the second step, salami-like were produced according to the individuated formulation and inoculated with the studied starters (10⁷ cfu/g); the fish mixture was stuffed into a natural casing and left to ferment at 30°C for 7 days. The use of the selected strains not only assured a correct fermentation but reduced the process time at only 2 days; during refrigerated storage, a good microbiological, chemico-physical and sensorial quality of the final product was recorded for at least 21 days.

Functional in vitro screening of probiotic strains for inoculation of piglets as a prophylactic measure towards Enterotoxigenic Escherichia coli infection

Enterotoxigenic Escherichia coli (ETEC), being the major cause of post-weaning diarrhoea (PWD) in newly weaned piglets, induces poor performance and economic losses in pig production. This functional in vitro screening study investigated probiotic strains for use in suckling piglets as a prophylactic strategy towards PWD. Nine strains were evaluated based on their ability to: enhance intestinal epithelial barrier function, reduce adherence of ETEC F18 to intestinal cells, inhibit growth of ETEC F18, and grow on porcine milk oligosaccharides. Strains included in the screening were of the species Lactobacillus, Enterococcus, Bifidobacterium and Bacillus. Our in vitro screening demonstrated genus-, species and strain-specific differences in the mode of action of the tested probiotic strains. Some of the tested bifidobacteria were able to grow on the two porcine milk oligosaccharides, 3'-sialyllactose sodium salt (3'SL) and Lacto-N-neotetraose (LNnT), whereas most lactic acid bacteria strains and both Bacillus subtilis strains failed to do so. All probiotic strains inhibited growth of ETEC F18 on agar plates. All but the bifidobacteria reduced binding of ETEC F18 to Caco-2 cell monolayers, with the Enterococcus faecium strain having the most profound effect. All three lactic acid bacteria and Bifidobacterium animalis subsp. lactis counteracted the ETEC F18-induced permeability across Caco-2 cell monolayers with the E. faecium strain exhibiting the most pronounced protective effect. The findings from this in vitro screening study indicate that, when selecting probiotic strains for suckling piglets as a prophylactic strategy towards PWD, it would be advantageous to choose a multi-species product including strains with different modes of action in order to increase the likelihood of achieving beneficial effects in vivo.

Assembly of propylene glycol alginate/β-lactoglobulin composite hydrogels induced by ethanol for co-delivery of probiotics and curcumin

Probiotics and curcumin can exhibit synergistic biological activities on the basis of a gut-brain axis, but are sensitive to environmental conditions, making it a challenge for their co-utilization. To meet the demand for high efficiency and convenience, both probiotics and curcumin were encapsulated within a propylene glycol alginate-based hydrogel delivery system, which was assembled using an ethanol-induced approach. The composite hydrogel was effective at sustaining the release of curcumin and protecting LGG cells in simulated gastrointestinal tract conditions. Moreover, it could also largely reduce the chemical degradation of curcumin and increase the survival of LGG during light exposure and long-term storage: up to 91.3 % of curcumin and 9.72 log CFU cm^-3 remained present throughout 4 weeks of storage. Results in this work demonstrate a low-energy and green approach to assemble a composite hydrogel with remarkable biocompatibility, which is considered as a desired delivery vehicle for co-delivery of probiotics and curcumin.

Identification of the key physiological characteristics of Lactobacillus plantarum strains for ulcerative colitis alleviation

Lactobacillus plantarum is a probiotic that is widely used to prevent ulcerative colitis (UC). However, the effects of this species are strain-specific. We believe that the physiological characteristics of L. plantarum strains may affect their UC-alleviating function. Therefore, this study investigated the relationship between the alleviating effect of L. plantarum strains on UC and their physiological characteristics in vitro. The physiological characteristics of 14 L. plantarum strains were assayed in vitro, including gastrointestinal transit tolerance, oligosaccharide fermentation, HT-29 cell adhesion, generation time, exopolysaccharide production, acetic acid production, and conjugated linoleic acid (CLA) synthesis. To create animal models, colitis was established in C57BL/6 mice by adding 3.5% dextran sulfate sodium to drinking water for 7 days. L. plantarum strains with significantly different physiological characteristics were orally administered to the mice at a dose of 3 × 109 CFU. The results indicated that among the tested L. plantarum strains, L. plantarum N13 and L. plantarum CCFM8610 significantly alleviated colitis in the mice, as observed from the restoration of the body weight and disease activity index (DAI) score, recovery of the gut microbiota composition, reduced expression of pro-inflammatory cytokines, and significantly inhibited expression of p65. Correlation analysis indicated that four of the measured physiological characteristics (gastrointestinal transit tolerance, HT-29 cell adhesion, generation time, and CLA synthesis) were related to the UC-alleviating effects to different degrees. The strongest correlation was observed between the CLA synthesis ability and UC-alleviating effects (with Pearson correlation coefficients for IL-1β, IL-6, IL-17F, TNF-α, myeloperoxidase, and the DAI all below -0.95). The ability to synthesize CLA may be the key physiological characteristic of L. plantarum in UC alleviation. Our findings may contribute to the rapid screening of lactic acid bacterial strains with UC-alleviating effects.

Lactobacillus plantarum L15 Alleviates Colitis by Inhibiting LPS-Mediated NF-κB Activation and Ameliorates DSS-Induced Gut Microbiota Dysbiosis

Previous studies have suggested that the Lactobacillus plantarum bacteria strain could be effective in ulcerative colitis (UC) management. However, its effects are strain-specific and the related mechanisms for its attenuating effects on UC remain unclear. This study aimed to elucidate the underlying mechanisms for the protective effect of L. plantarum on UC. Firstly, 15 L. plantarum strains were screened for potential probiotic characteristics with good tolerance to simulated human gastrointestinal transit and adhesion. Secondly, the inflammatory response of selected strains to the Caco-2 cells induced by lipopolysaccharide (LPS) was measured. Finally, an in vivo mouse model induced by dextran sulfate sodium (DSS) was used to assess the beneficial effects and likely action mechanisms the successfully screened in vitro strain, L. plantarum L15. In vitro results showed that L. plantarum L15 possessed the highest gastrointestinal transit tolerance, adhesion and reduction of pro-inflammatory abilities compared to the other screened strains. In vivo, high dose of L. plantarum L15 supplementation increased the body weight, colon length and anti-inflammatory cytokine production. Pro-inflammatory cytokine production, disease activity index (DAI) levels and myeloperoxidase (MPO) parameters decreased using this strain. In addition, L. plantarum L15 alleviated the histopathological changes in colon, modulated the gut microbiota, and decreased LPS secretion. The activities of this strain down-regulated the expression of TLR4 and MyD88 genes as well as genes associated with NF-κB signaling pathway. Our findings present L. plantarum L15 as a new probiotic, with promising application for UC management.

Dynamics of microbial communities, texture and flavor in Suan zuo yu during fermentation

Suan zuo yu is a traditional Chinese fermented product. We explored the microbial diversity, the dynamic changes of texture and flavor compounds at different fermentation times (up to 24 d). Results showed that Weissella and Lactobacillus may play a vital role in fermentation especially for the flavor. At the end of fermentation, the taste activity value of Asp, Glu, and His were 21.61, 17.29 and 7.73, respectively. The bound water increased gradually indicated by low-field nuclear magnetic resonance, and the hardness was also increased. During the whole fermentation process, the myosin heavy chain protein and actin decreased obviously. Gas chromatography-mass spectrometry showed that a total of 80 volatile compounds were detected, and 6 alcohols, 6 aldehydes and 6 esters increased significantly, which mainly contributed to the flavor of Suan zuo yu. This study provides a theoretical basis for the industrial production of fermented fish.

Characterization of a potential probiotic bacterium Lactococcus raffinolactis WiKim0068 isolated from fermented vegetable using genomic and in vitro analyses

Background

Lactococcus members belonging to lactic acid bacteria are widely used as starter bacteria in the production of fermented dairy products. From kimchi, a Korean food made of fermented vegetables, Lactococcus raffinolactis WiKim0068 was isolated and its genome was analyzed.

Results

The complete genome of the strain WiKim0068 consists of one chromosome and two plasmids that comprises 2,292,235 bp, with a G + C content of 39.7 mol%. Analysis of orthoANI values among Lactococcus genome sequences showed that the strain WiKim0068 has > 67% sequence similarity to other species and subspecies. In addition, it displayed no antibiotic resistance and can metabolize nicotinate and nicotinamide (vitamin B3).

Conclusion

These results augments our understanding of the genus Lactococcus and suggest that this new strain has potential industrial applications.

Bioprospecting of probiotics with antimicrobial activities against Salmonella Heidelberg and that produce B-complex vitamins as potential supplements in poultry nutrition

The demand for animal protein for human consumption has been risen exponentially. Modern animal production practices are associated with the regular use of antibiotics, potentially increasing the emerging multi-resistant bacteria, which may have a negative impact on public health. In poultry production, substances capable of maximizing the animals’ performance and displaying an antimicrobial activity against pathogens are very well desirable features. Probiotic can be an efficient solution for such a task. In the present work, lactic acid bacteria (LAB) were isolated from chicken cecum and screened for their antagonistic effect towards many pathogens. Their capacity of producing the B-complex vitamins folate and riboflavin were also evaluated. From 314 isolates, three (C43, C175 and C195) produced Bacteriocin-Like Inhibitory Substances (BLIS) against Staphylococcus aureus (inhibition zones of 18.9, 21.5, 19.5 mm, respectively) and also inhibited the growth of Salmonella Heidelberg. The isolate C43 was identified as Enterococcus faecium, while C173 and C195 were both identified as Lactococcus lactis subsp. lactis. Moreover, the isolates L. lactis subsp. lactis strains C173 and C195 demonstrated high potential to be used as probiotic in poultry feed, in addition to their advantage of producing folate (58.0 and 595.5 ng/mL, respectively) and riboflavin (223.3 and 175.0 ng/mL, respectively).

The Biotherapeutic Potential of Lactobacillus reuteri Characterized Using a Target-Specific Selection Process

A growing body of clinical and experimental data supports the view that the efficacy of probiotics is strain-specific and restricted to particular pathological conditions, which means that newly isolated probiotic strains need to be targeted to a specific disease. Following national and international guidelines, we used a conventional in vitro experimental approach to characterize a novel strain of Lactobacillus reuteri, LMG P-27481, for safety (sensitivity to antibiotics and genome analysis) and putative efficacy (resistance to gastro-intestinal transit, adhesiveness, induction of cytokines, and release of antimicrobial metabolites). In vitro assays, which were carried out to examine the probiotic's effect on diarrhea (lactose utilization, inhibition of pathogens such as bacteria and Rotavirus), showed that it was more efficacious with respect to well-known reference strains in antagonizing Clostridioides difficile (CD). Data confirming that the probiotic can effectively treat CD colitis was gained from in vivo trials involving mice conditioned with large spectrum antibiotics before they were subjected to CD challenge. Two out of the three antibiotic-treated groups received daily LMG P-27481 for different time durations in order to simulate a preventive approach (LMG P-27481 administered prior to CD challenge) or an antagonistic one (LMG P-27481 administered after CD challenge). Both approaches significantly reduced, with respect to the untreated controls, CD DNA concentrations in caecum and C. difficile toxin titers in the gut lumen. In addition, LMG P-27481 supplementation significantly mitigated body weight loss and the extent of inflammatory infiltrate and tissue damage. The study results, which need to be confirmed by in vivo clinical trials, have demonstrated that the L. reuteri LMG P-27481 strain is a promising probiotic candidate for the treatment of CD infection.

Whole genome sequence analysis and in vitro probiotic characteristics of a Lactobacillus strain Lactobacillus paracasei ZFM54

AIM

The aim was to identify a Lactobacillus strain with potential probiotic characteristics by whole-genome sequence analysis and in vitro experimental studies.

METHODS AND RESULTS

The whole-genome sequencing was carried out using PacBio RSII sequencing method and Illumina's paired-end sequencing technology. Gene prediction and annotation were achieved using GlimmerVersion 3.02 and NCBI prokaryotic Genome Annotation Pipeline. Identification was done by biochemical tests and 16S rRNA sequence analysis. mega 6 software was used to build phylogenetic tree. Antagonism against pathogen was determined by agar well diffusion method. Resistance and stability to bile, simulated gastric acid, different salt concentration and thermostability were investigated. Hydrophobicity assay, aggregation assay and anti-oxidation assay were performed to check further probiotic traits. Finally antibiotic susceptibility and acute oral toxicity of the strain in mice were investigated to check its safety status. The strain showed >99% similarity to Lactobacillus paracasei which was further confirmed by biochemical tests. It significantly inhibited pathogens in agar well diffusion assay. It showed tolerance to simulated gastric acid (pH 3), 0·3% bile salt and 10% NaCl. Significant hydrophobic, aggregation and anti-oxidizing activities were observed. No resistance to antibiotics tested was observed and no adverse effects during acute oral toxicity in mice were detected.

CONCLUSIONS

Lactobacillus paracasei ZFM 54, a new and safe Lactobacillus strain was identified with numerous probiotic-associated genes and characteristics confirmed by experimental studies.

SIGNIFICANCE AND IMPACT OF THE STUDY

A new probiotic strain has been identified which is highly stable, safe and suitable to be used in health and food industries.

How to Assess in vitro Probiotic Viability and the Correct Use of Neutralizing Agents

Probiotic viability is generally determined by quantifying its resistance to simulated gastric juice or to simulated intestinal fluid in in vitro tests, which measure microbial survival after given periods of contact. The use of a neutralizing agent is needed to avoid a carry-over of gastric or intestinal juice into the culture media of the subsequent analysis and to avoid any antimicrobial effect extended over the defined period of contact of the test. Neutralization of gastric juice and intestinal juice are of the utmost importance to present data accurately. Failing to do so determines a carry-over of bactericidal activity to the plates used for the enumeration, which further reduces the number of surviving cells. Examples of such incorrect adaptation of the test are available in literature. The purpose of this perspective stems from the discovery that many studies do not adhere to internationally recognized standards, e.g., EN 1040:2005 (European Committee for Standardization [ECS], 2005), to evaluate the basic, bactericidal activity of compounds, especially for the neutralization step.

Quantifying and Engineering Mucus Adhesion of Probiotics

Mucus in the gastrointestinal (GI) tract is the primary point-of-interaction between humans and their gut microbiota. This intimates that mucus not only ensures protection against endogenous and exogenous opportunists but also provisions for the human microbiota to reside and flourish. With the emergence of living therapeutics, engineered microbes can deliver and produce increasingly complex medicine, and controlling the mucoadhesive properties of different microbial chassis can dictate dose-response in a patient. Here we present a redesigned, in vitro, plate-based assay to measure the mucus adhesion of various probiotics. Cell-mucus interactions were isolated by immobilizing mucus to the plate surface. Binding parameters were derived for each probiotic strain by measuring cell adhesion over a wide range of cell concentrations, providing dose-dependent adhesion metrics. Surface proteins and cell components known to influence mucoadhesion were then heterologously expressed or altered in Lactococcus lactis MG1363 and Escherichia coli Nissle 1917 to control mucus-binding capacity, avidity, and cooperativity.

Structural characterisation of two medium molecular mass exopolysaccharides produced by the bacterium Lactobacillus fermentum Lf2

Under optimized conditions, the lactic acid bacterium Lactobacillus fermentum Lf2 secretes up to 2 gL^-1 of a mixture of polysaccharides into the fermentation medium when grown on sucrose. Earlier studies had shown that the mixture is biologically active and work was undertaken to characterise the polysaccharides. Preparative size exclusion chromatography was used to separate a high molecular mass β-glucan (weight average mass of 1.23 × 10⁶ gmol^-1) from two medium molecular mass polysaccharides (weight average mass of 8.8 × 10⁴ gmol^-1). Under optimized growth conditions, the medium molecular mass polysaccharides accounted for more than 75% of the mixture by weight. Monomer, linkage analysis and NMR spectroscopy of the medium molecular mass polysaccharides, and material isolated after their Smith degradation, was used to identify the structure of the component polysaccharides. The mixture contains two novel polysaccharides. The first has a main chain of β-1,6-linked galactofuranoses which is non-stoichiometrically 2-O-glucosylated. The degree of substitution at the 2-position, with α-D-Glcp, depends on the fermentation conditions; under optimized conditions greater than 80% 2-O-α-D-glucosylation was observed. The second polysaccharide is a heteroglycan with four monosaccharides in the repeat unit: residual signals in the NMR suggest that the sample also contains trace amounts (<3%) of cell wall polysaccharides.

Functional Properties of Food Origin Lactobacillus in the Gastrointestinal Ecosystem-In Vitro Study

In the current study, the probiotic activity of ten Lactobacillus (Lb.) strains, previously isolated from the traditional Polish fermented vegetable, was characterized. Strains were assessed for adhesion to human intestinal epithelial Caco-2 cells and regulation of selected cytokine production (IL-1β, IL-6, IL-10, IL-23, and TNF-α) by THP-1 macrophages. The effect of tested strains on Caco-2 cell apoptosis was also investigated using a caspase-3 assay. Adhesion capacity was strain-dependent (1.29-8.24% of initial population). Highest adhesion was observed for Lb. brevis O24. All Lactobacillus strains investigated in this study stimulated two- to threefold increase in TNF-α, IL-1β, and IL-6 production, compared to the control. Additionally, selected strains of Lactobacillus caused a significant decrease of pro-inflammatory cytokine production by lipopolysaccharide (LPS)-stimulated THP-1 cells. Almost all Lactobacillus investigated in this study are potent stimulators of IL-10 production. All tested Lactobacillus cells slightly increased the caspase-3 activity in Caco-2 cells. Lb. casei O18 was the most inducing strain. The tested strains had no effect on staurosporine (STS)-induced caspase-3 activity. According to these results, the most promising strains are Lb. plantarum O20, two strains Lb. brevis O22 and O24, and Lb. rhamnosus K3. These newly identified lactobacilli hold promise for use as probiotics in functional food applications.