Brevis Strain Research Articles

Comprehensive genomic analysis of Brevibacillus brevis BF19 reveals its biocontrol potential against bitter gourd wilt

Bitter gourd wilt, a severe vascular disease triggered by the soilborne pathogen Fusarium oxysporum f. sp. momordicae (FOM), markedly constrains bitter gourd yield. In this study, a novel strain BF19 of Brevibacillus brevis was isolated and identified, exhibiting strong antimicrobial activity against FOM through in vivo and in vitro experiments. To comprehensively assess the biocontrol potential of strain BF19, we conducted phenotypic, phylogenetic, and comparative genomics analyses. Phenotypic analysis revealed that BF19 exhibited 53.33% biocontrol efficacy and significantly increased the average plant height, root fresh weight, and dry weight. Whole-genome sequencing and comparative genomic analysis revealed numerous potential genes associated with biocontrol mechanisms in BF19. Importantly, the integration of metabolic cluster prediction with liquid chromatography‒tandem mass spectrometry (LC‒MS/MS) revealed the presence of a macrobrevin antibiotic, a product of polyketide synthases (PKSs), predominantly in BF19 fermentation products. The effectiveness of the Br. brevis strain BF19 and its crude extract against bitter gourd wilt has also been confirmed. This study provides a genetic framework for future investigations on PKSs and establishes a scientific basis for optimizing field applications of microbial biopesticides derived from Br. brevis BF19.

Isolation and Characterization of Bacteriocin Producing Levilactobacillus brevis Strain ABRIINW-K from Buffalo Dung

Bacteriocins are proteins secreted by many species of bacteria to inhibit other bacteria, thus eliminating competitors to gain resources. Bacteria from the Lactobacillus group are known for their applications as probiotics and food preservatives. They have earned a reputation for producing substances that inhibit the growth of other microorganisms, which include organic acids, diacetyl, and bacteriocins. Produced by the ribosomes, bacteriocins are cationic proteins that inhibit other bacteria coexisting within a shared ecological habitat. Due to their potential uses in a variety of applications large-scale production of Bacteriocins would be necessary. The study aimed to identify and characterize Lactobacillus bacteria that produce potent bacteriocins and to analyze the antimicrobial activity and stability of the isolated bacteriocin under various physical and biochemical conditions. A total of 50 samples including buffalo dung, cheese, and rhizospheric region of plants were screened to isolate 8 Lactobacillus Li-1, Li-2, Li-3, Li-4, Li-5, Li-6, Li-7, and Li-8, confirmed by gram staining and other biochemical tests. The cell free supernatant from the Li-3 strain showed higher inhibition of Escherichia coli and Staphylococcus aureus, as compared to the other isolated strains. Li-3 strain was further identified as Levilactobacillus brevis strain ABRIINW-K by 16S rRNA gene sequencing. The bacteriocin isolated from this strain is a thermostable peptide (~6kDa), which is characteristic of class II bacteriocins, with potent antibacterial activity against Lactobacillus rhamnosus, Escherichia coli, and Salmonella enterica.

Heat-killed probiotic Levilactobacillus brevis MKAK9 and its exopolysaccharide promote longevity by modulating aging hallmarks and enhancing immune responses in Caenorhabditis elegans

BackgroundProteostasis is a critical aging hallmark responsible for removing damaged or misfolded proteins and their aggregates by improving proteasomal degradation through the autophagy-lysosome pathway (ALP) and the ubiquitin–proteasome system (UPS). Research on the impact of heat-killed probiotic bacteria and their structural components on aging hallmarks and innate immune responses is scarce, yet enhancing these effects could potentially delay age-related diseases.ResultsThis study introduces a novel heat-killed Levilactobacillus brevis strain MKAK9 (HK MKAK9), along with its exopolysaccharide (EPS), demonstrating their ability to extend longevity by improving proteostasis and immune responses in wild-type Caenorhabditis elegans. We elucidate the underlying mechanisms through a comprehensive approach involving mRNA- and small RNA sequencing, proteomic analysis, lifespan assays on loss-of-function mutants, and quantitative RT-PCR. Mechanistically, HK MKAK9 and its EPS resulted in downregulation of the insulin-like signaling pathway in a DAF-16-dependent manner, enhancing protein ubiquitination and subsequent proteasomal degradation through activation of the ALP pathway, which is partially mediated by microRNA mir-243. Importantly, autophagosomes engulf ubiquitinylated proteins, as evidenced by increased expression of the autophagy receptor sqst-3, and subsequently fuse with lysosomes, facilitated by increased levels of the lysosome-associated membrane protein (LAMP) lmp-1, suggesting the formation of autolysosomes for degradation of the selected cargo. Moreover, HK MKAK9 and its EPS activated the p38 MAPK pathway and its downstream SKN-1 transcription factor, which are known to regulate genes involved in innate immune response (thn-1, ilys-1, cnc-2, spp-9, spp-21, clec-47, and clec-266) and antioxidation (sod-3 and gst-44), thereby reducing the accumulation of reactive oxygen species (ROS) at both cellular and mitochondrial levels. Notably, SOD-3 emerged as a transcriptional target of both DAF-16 and SKN-1 transcription factors.ConclusionOur research sets a benchmark for future investigations by demonstrating that heat-killed probiotic and its specific cellular component, EPS, can downregulate the insulin-signaling pathway, potentially improving the autophagy-lysosome pathway (ALP) for degrading ubiquitinylated proteins and promoting organismal longevity. Additionally, we discovered that increased expression of microRNA mir-243 regulates insulin-like signaling and its downstream ALP pathway. Our findings also indicate that postbiotic treatment may bolster antioxidative and innate immune responses, offering a promising avenue for interventions in aging-related diseases.

Molecular characterization and multifunctional evaluation of lactic acid bacteria isolated from traditional sourdough

The primary objective of this study was to characterize lactic acid bacteria (LAB) strains derived from sourdough for possible utilization as functional starters to produce sourdough and various cereal-based fermented foods. A total of 350 autochthonous LAB strains were isolated from 65 Type I sourdough samples and characterized using six random amplified polymorphic DNA (RAPD) primers at intra- and interspecific levels. Species identification of selected strains representing distinct clusters from RAPD analysis was performed based on the 16S rRNA region. The LAB strains were identified as Companilactobacillus crustorum (n = 135), Levilactobacillus brevis (n = 125), Latilactobacillus curvatus (n = 40), Companilactobacillus paralimentarius (n = 32), and Lactiplantibacillus plantarum (n = 18). A total of 66 LAB strains were selected for technological characterization along with two commercial strains. The characterization involved acidity development, EPS production potential, leavening activity, and growth abilities under harsh conditions. Principle component analysis (PCA) identified 2 Lp. plantarum and 14 Lev. brevis strains as the most relevant technologically. Among them, Lp. plantarum L35.1 and Lev. brevis L37.1 were resistant to tetracycline. Evaluation of probiotic characteristics (survival in pH 2.5 and bile presence, auto aggregation capacity, hydrophobic activity, antioxidant activity, antimicrobial activity) by PCA identified four strains with relevance to Lactobacillus rhamnosus GG (LGG), which were further selected for in vitro digestion assays. Lactiplantibacillus plantarum L7.8, Lev. brevis L55.1, and L62.2 demonstrated similar viability indices to LGG, along with increased auto aggregation capacity and antioxidant activity. These strains are promising as candidate starters for producing sourdough and sourdough-related fermented food products.

Biofortification, metabolomic profiling and quantitative analysis of vitamin B12 enrichment in guava juice via lactic acid fermentation using Levilactobacillus brevis strain KU15152.

Chemical fortification and dose supplementation of vitamin B12 are widely implemented to combat deficiency symptoms. However, in situ, fortification of vitamin B12 in food matrixes can be a promising alternative to chemical fortification. The present study aimed to produce vitamin B12-rich, probiotic guava juice fermented with Levilactobacillus brevis strain KU15152. Pasteurized fresh guava juice was inoculated with 7.2 log CFU mL-1 L. brevis strain KU15152 and incubated for 72 h at 37 °C anaerobically. The antioxidants, total phenolic compounds, vitamin B12 production, sugars, organic acids, pH and viable count were analyzed at 24, 48 and 72 h of incubation. The fermented juice was stored at 4 °C, and the changes in its functional properties were analyzed at 7-day intervals up to 28 days of storage. During fermentation, the bacteria cell count was increased from 7.01 ± 0.06 to 9.76 ± 0.42 log CFU mL-1 after 72 h of fermentation and was decreased to 6.94 ± 0.34 CFU mL-1 during storage at 4 °C after 28 days. The pH, total soluble solids, crude fiber, citric acid and total sugars decreased, while titratable acidity, total protein, antioxidants, phenolic compounds and lactic acid contents increased during fermentation. The fermented guava juice exhibited higher 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS)) radical scavenging activities (85.97% and 75.97%, respectively) at 48 h of fermentation. The concentration of active vitamin B12 in the sample reached 109.5 μg L-1 at 72 h of fermentation. However, this concentration gradually decreased to 70.2 μg L-1 during the storage period. During storage for 28 days at 4 °C, both the fermented and control guava juices exhibited a decline in antioxidant and phenolic compound concentrations. Furthermore, the addition of 20% honey and guava flavor enhanced the organoleptic properties and acceptability of fermented guava juice. The value-added fermented guava juice could be a novel functional food product to combat vitamin B12 deficiency. © 2024 The Author(s). Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Mechanism of Brevibacillus brevis strain TR-4 against leaf disease of Photinia×fraseri Dress.

Colletotrichum species are among the most common pathogens in agriculture and forestry, and their control is urgently needed. In this study, a total of 68 strains of biocontrol bacteria were isolated and identified from Photinia × fraseri rhizosphere soil. The isolates were identified as Brevibacillus brevis by 16S rRNA. The inhibitory effect of TR-4 on Colletotrichum was confirmed by an in vitro antagonistic experiment. The inhibitory effect of TR-4 was 98% at a concentration of 10 µl/ml bacterial solution, protection of the plant and inhibition of C. siamense was evident. Moreover, the secretion of cellulase and chitosan enzymes in the TR-4 fermentation liquid cultured for three days was 9.07 mol/L and 2.15 µl/mol, respectively. Scanning electron microscopy and transmission electron microscopy confirmed that TR-4 destroyed the cell wall of C. siamense, resulting in leakage of the cell contents, thus weakening the pathogenicity of the bacteria.

S-layer proteins in microencapsulated freeze-dried probiotic Levilactobacillus brevis strains

The presence of surface (S)-layer proteins as a rare property of lactic acid bacteria plays an important role in the expression of the probiotic properties of the producer strain and protects the cells from unfavourable environmental conditions. Therefore, the aim of this work was to evaluate the role of S-layer proteins of four Levilactobacillus brevis MB1, MB2, MB13, and MB20 strains, previously isolated from human milk. The results showed better survival under simulated gastrointestinal tract (GIT) conditions and better adhesion to Caco-2 cells, achieved when S-proteins were present on the surface of the examined probiotic Levilactobacillus brevis strains. Free cells and cells microencapsulated in alginate, with or without galactooligosaccharides (GOS) and fructooligosaccharides (FOS), survived in high numbers during freeze-drying and one-month storage at 4 °C, as well as during exposure to simulated GIT conditions (>108 CFU/g), thus fulfilling the primary technological criterion for the selection of probiotic strains. Higher survival of freeze-drying of encapsulated cells than free cells, can be attributed to the protective effect of alginate, GOS and FOS as prebiotic agents. However, GOS was more protective than FOS in maintaining the viability of microencapsulated Levilactobacillus brevis MB1, MB2, MB13 and MB20 cells in alginate during storage and under the harsh conditions of GIT and freeze-drying.

Pan-Genome Analysis and Secondary Metabolic Pathway Mining of Biocontrol Bacterium Brevibacillus brevis

Brevibacillus brevis is one of the most common biocontrol strains with broad applications in the prevention and control of plant diseases and insect pests. In order to deepen our understanding of B. brevis genomes, describe their characteristics comprehensively, and mine secondary metabolites, we retrieved the genomic sequences of nine B. brevis strains that had been assembled into complete genomes from the NCBI database. These genomic sequences were analyzed using phylogenetic analysis software, pan-genome analysis software, and secondary metabolite mining software. Results revealed that the genome size of B. brevis strains ranged from 6.16 to 6.73 Mb, with GC content ranging from 47.0% to 54.0%. Phylogenetic analysis classified the nine B. brevis strains into three branches. The analyses of ANI and dDDH showed that B. brevis NEB573 had the potential to become a new species of Brevibacillus and needed further research in the future. The pan-genome analysis identified 10032 gene families, including 3257 core gene families, 3112 accessory gene families, and 3663 unique gene families. In addition, 123 secondary metabolite biosynthetic gene clusters of 20 classes were identified in the genomes of nine B. brevis strains. The major types of biosynthetic gene clusters were non-ribosomal peptide synthase (NRPS) and transAT polyketide synthase (transAT-PKS). Furthermore, a large number of untapped secondary metabolites were identified in B. brevis. In summary, this study elucidated the pan-genome characteristics of the biocontrol bacterium B. brevis and identified its secondary metabolites, providing valuable insights for its further development and utilization.

Production and quality evaluation of a novel γ-aminobutyric acid-enriched yogurt.

γ-aminobutyric acid (GABA) is a neurotransmitter inhibitor that has beneficial effects on various health conditions such as hypertension, cognitive dysfunction, and anxiety. In this study, we investigated a novel yogurt naturally enriched with GABA using a Levilactobacillus brevis strain isolated in our laboratory; the specific optimum yogurt production conditions for this strain were determined. We isolated an L. brevis strain and used it to produce yogurt naturally enriched with GABA. We explored the optimal conditions to enhance GABA yield, including fermentation temperature, inoculation amount, L-monosodium glutamate (L-MSG) concentration, fermentation time, and sucrose content. We also performed mixed fermentation with Streptococcus thermophilus and evaluated the quality of the yogurt. Following optimization (43°C, 8% inoculation amount, 1.5 g/L L-MSG, and 8% sucrose for 40 h of fermentation), the GABA yield of the yogurt increased by 2.2 times, reaching 75.3 mg/100 g. Mixed fermentation with S. thermophilus demonstrated favorable results, achieving a GABA yield akin to that found in some commercially available functional foods. Moreover, the viable microbe count in the GABA-enriched yogurt exceeded 1 × 108 cfu/mL, which is higher than that of commercial standards. The yogurt also exhibited a suitable water-holding capacity, viscosity, 3-week storage time, and favorable sensory test results. This study highlights the potential of naturally enriched GABA yogurt as a competitive commercial yogurt with beneficial health effects.

Supplementation with Lactiplantibacillus brevis GKEX Combined with Resistance Exercise Training Improves Muscle Mass, Strength Performance, and Body Fat Condition in Healthy Humans.

In addition to maintaining good exercise and dietary habits, recent studies have shown that probiotics may have potential benefits for muscle mass and strength. It is worth noting that the effects may vary depending on the specific strains used. To date, no studies have analyzed the effects of Lactiplantibacillus brevis in this context. Here, we combine the L. brevis strain GKEX with resistance training to further understand its effects on muscle mass, thickness, performance, and fat loss. In a six-week intervention for a double-blind randomized trial, 52 healthy subjects were divided into two groups (10 male and 16 female participants in each group): a placebo group (two capsules/day, containing 0 CFU of GKEX per capsule) and a GKEX group (two capsules/day, containing 1 × 1010 CFU of GKEX per capsule). Before the intervention, no differences were observed between the two groups in any of the tests (body composition, muscle thickness, exercise performance, and blood parameters). However, supplementation with GKEX significantly improved muscle mass and thickness, as well as grip strength, muscle strength, and explosive performance, when compared to the associated parameters before the intervention. Additionally, GKEX supplementation promoted a reduction in the body fat percentage (p < 0.05). Through analysis of the change amount, we observed that GKEX supplementation yielded significantly improved benefits when compared to the placebo group (p < 0.05). In summary, our findings support the notion that a six-week resistance exercise training program combined with L. brevis GKEX supplementation has superior additive effects that enhance muscle mass and strength performance, while also reducing body fat percentage. This intervention can promote muscle gain and fat loss.

Traditional Bulgarian Fermented Foods as a Source of Beneficial Lactic Acid Bacteria.

Traditional Bulgarian fermented foods are prominent for their uniqueness of local ingredients, production methods, and endemic microbial species. The present research investigated the diversity and beneficial biological potential of lactic acid bacteria (LAB) isolated from various types of unique Bulgarian fermented foods. Species identification was performed via 16S rDNA sequencing. Biological activity was evaluated by determining antibacterial activity (via agar well diffusion assay), H2O2 production, spectrophotometrically determined auto- and co-aggregation, microbial adhesion to hydrocarbon, and biofilm formation. The biosafety of the isolated lactic acid bacteria was established based on hemolytic activity and phenotypic and genotypic antibiotic susceptibility. Forty-five strains were isolated from fermented foods (sauerkraut, fermented green tomatoes, fermented cucumbers, kefir, white cheese, and Izvara (curdled milk)). Five species were detected: Lactiplantibacillus plantarum, Levilactobacillus koreensis, Levilactobacillus brevis, Lactobacillus helveticus, and Levilactobacillus yonginensis. The most prominent species was L. plantarum, at 47%. For the first time, L. koreensis and L. yonginensis, isolated from unique Bulgarian fermented foods, are reported in this study. The antibacterial effect of the cell-free supernatants was evaluated. An antagonistic effect was observed against Escherichia coli (57%) and Salmonella enterica subsp. enterica serotype Enteritidis (19%) for several L. plantarum strains. Only one L. brevis (Sauerkraut, S15) strain showed activity against E. coli. The best autoaggregation ability at hour 4 was observed for L. koreensis (fermented cucumbers, FC4) (48%) and L. brevis S2 (44%). The highest percentage of co-aggregation with Candida albicans, at hou 4 in the experiments, was observed for strains L. koreensis (fermented green tomato, FGT1) (70%), L. plantarum strains S2 (54%), S13 (51%), and S6 (50%), while at hour 24 for strains L. koreensis FGT1 (95%), L. brevis (Kefir, K7) (89%), L. plantarum S2 (72%), and L. koreensis FC2 (70%). Seven of the isolated LAB strains showed hydrophobicity above 40%. Our results showed that the ability of biofilm formation is strain-dependent. No hemolytic activity was detected. The antibiotic resistance to 10 antibiotics from different groups was tested phenotypically and genotypically. No amplification products were observed in any strains, confirming that the isolates did not carry antibiotic-resistance genes. Traditional fermented Bulgarian foods can be considered functional foods and beneficial LAB sources.

Biosorption and Bioprotective Potential of Levilactobacillus brevis in Mice Challenged by Lead-Induced Oxidative Stress.

Lead (Pb) poisoning is a widespread issue in both developed and developing countries that poses a significant public health challenge. Our study aimed to explore the impact of Levilactobacillus brevis strains on inflammatory and antioxidant gene expression in the liver and brain of mice exposed to oxidative stress caused by Pb. We began by evaluating Pb absorption by Levilactobacillus brevis strains (ARKA-CH-1 (A1) and ARKA-CH-6 (A6)) using the inductively coupled plasma mass spectrometry (ICP-MS) in vitro to identify the most effective strain. We then divided four groups of BALB/c mice into control and experimental groups and treated them for 30days. The control group received a normal diet, while the experimental groups consumed lead-containing water (0.6g/L) with or without Levilactobacillus brevis strains. Following the experiments, we collected blood samples to test liver markers, antioxidant enzymes, and immunoglobulins. We also used real-time PCR to examine the expression of superoxide dismutase (SOD) and inducible nitric oxide synthase (iNOS) genes. The results showed that the A1 strain was the most effective in absorbing Pb. The Pb exposure led to an increase in liver enzyme values and a decrease in antioxidant enzyme activity and immunoglobulin factors. However, the combination of A1 and A6 strains had a greater effect in reducing inflammatory enzymes and increasing antioxidant enzymes. Furthermore, we observed a significant increase in iNOS gene expression and a notable decrease in SOD gene expression with Pb consumption. However, the combination of A1 and A6 strains had a synergistic effect in reducing iNOS and increasing SOD gene expression. In conclusion, Levilactobacillus brevis A1 strain alone or in combination with the A6 strain could be a promising strategy to mitigate the oxidative stress symptoms in mice challenged by lead-induced toxicity.

Results of the study on the antimicrobial activity of probiotic strains of lactobacilli and their potential application in feed formulations for aquaculture species

A comparative analysis of the antibacterial activity of authentic strains of lactobacilli was conducted. Primary data on the antibacterial activity of Lactobacillus acidophilus, L. brevis, and L. plantarum were obtained, as well as the impact of L. brevis in the composition of the extruded feed «BioMar» on the physiological condition of juvenile rainbow trout. The supplement was orally introduced into the main diet at a concentration of 2×108 cells of L. brevis per milligram of feed for 30 days. The obtained results were evaluated based on changes in the growth indicators, survival rates, and the diversity of the background microflora in the intestinal contents of trout fry in the experimental and control groups. According to the experiment results, the physiological indicators of trout fry receiving the premix with lactobacilli in the feed were higher than those in the control group. In the intestinal contents of the experimental group, a high proportion of lactobacilli (9.4%) was maintained, unlike the control group, which was on a diet without any additives (average values of lactobacilli in the intestinal contents did not exceed 0.6%). The studied biological properties of the Lactobacillus brevis strain make it a potential probiotic culture for use in therapeutic and prophylactic feed formulations for aquaculture.

Effect of Fortified Inoculation with Indigenous Lactobacillus brevis on Solid-State Fermentation of Light-Flavor Baijiu.

Baijiu, one of the world's oldest distilled liquors, is widely consumed globally and has gained increasing popularity in East Asia. However, a comprehensive understanding of the underlying principles behind this traditional liquor product remains elusive. Currently, Baijiu is facing the industrial challenge of modernization and standardization, particularly in terms of food quality, safety, and sustainability. The current study selected a Lactobacillus brevis strain based on experiments conducted to assess its environmental tolerance, enzyme activity, and fermentation performance, and highlight its exceptional fermentation characteristics. The subsequent analysis focused on examining the effects of fortifying the fermentation process of L.brevis on key microbiotas, physicochemical parameters, and volatile profiles. The qPCR results revealed that the inoculated L. brevis strategically influenced the the composition of the dominant microbial communities by promoting mutual exclusion, ultimately leading to improved controllability of the fermentation process. Moreover, the metabolism of the inoculated L. brevis provided more compounds for the formation of flavor profiles during fermentation (the content of ethyl acetate was increased to 57.76 mg/kg), leading to a reduction in fermentation time (from 28 d to 21 d). These findings indicate promising potential for the application of the indigenous strain in Baijiu production.

Production of xylo-oligosaccharides with degree of polymerization 3–5 from wheat straw xylan by a xylanase derived from rumen metagenome and utilization by probiotics

In this study, a new xylanase gene (RuXyn) was obtained from a rumen metagenome and heterologously expressed in Escherichia coli to produce xylo-oligosaccharides (XOS) as a prebiotic. RuXyn, which belongs to the glycosyl hydrolase 10 (GH10) family, exhibited maximum activity at pH 6.0 and 50 °C, with excellent temperature resistance at 30–50 °C. RuXyn showed preferential hydrolysis of xylan, especially rice straw xylan. RuXyn activity was significantly increased in the presence of 5 mM dithiothreitol, 0.5% Tween-20, and 0.5% Triton X-100 (31%, 37%, and 43%, respectively). Reaction time (10, 15, 30, and 45 min) and dosage (0.15, 0.31, and 0.62 U) of RuXyn affected XOS yield and composition, with a maximum yield at 0.62 U and 30 min. The primary degradation products of wheat straw xylan, resulting from RuXyn activity, were xylotetraose, xylotriose, and xylopentose, which accounted for 33.4%, 33.0%, and 26.4% of the total sugar yield, respectively. The prebiotic effects of XOS were evaluated by in vitro fermentation of XOS using known probiotic Bifidobacterium bifidum and Levilactobacillus brevis strains. Results showed that regardless of incubation time and XOS concentration, XOS stimulated the growth and xylanolytic enzyme secretion of the two probiotics compared to the controls. Supplementation with XOS significantly enhanced lactate production in B. bifidum and L. brevis. Thus, these results indicate that RuXyn is capable of hydrolyzing wheat xylan to produce XOS with a degree of polymerization 3 and 5 and to subsequently promote the growth of probiotics.

Biological Control of Grapevine Powdery Mildew Disease by Using Brevibacillus brevis Strain CP-1

Biological Control of Grapevine Powdery Mildew Disease by Using Brevibacillus brevis Strain CP-1

Characterization of potential probiotic and safety properties of Levilactobacillus brevis isolated from traditionally fermented milk, Amabere amaruranu

The study aimed to determine the probiotic and safety properties of a bacterial strain isolated from Kenyan traditionally fermented milk called Amabere amaruranu. Probiotic characteristics of the isolate were assessed based on its ability to survive artificial simulated conditions of the digestive tract including temperature sensitivity, low pH and phenol tolerance, and antagonistic activity against human bacterial (Staphylococcus aureus, Escherichia coli, and Salmonella enterica Typhimurium) and fungal (Candida albicans) pathogens. Safety analysis was based on hemolytic activity and antibiotic susceptibility against most common antibiotics namely: nalidixic acid, ampicillin, azithromycin, ciprofloxacin, tetracycline, gentamicin, and chloramphenicol using zone of diameter of inhibition (ZDI). The isolate survived and grew in low pH (2.0–3.5), tolerated 0.4% phenol, and survived temperature ranges of 20°C, 30°C, and 37°C but showed partially reduced growth at 45°C. It exhibited strong antagonism against all pathogens (ZDI&gt;20 mm). Antagonism was strongest towards S. enterica serovar Typhimurium (ZDI = 59 mm) and lowest towards E. coli (ZDI = 33 mm). The isolate was sensitive to azithromycin (ZDI = 31± 2.08), chloramphenicol (ZDI = 26 ±2.34 mm), gentamycin (ZDI = 26 ±1.41mm), and tetracycline (ZDI = 32 ±1.73 mm), resistant to nalidixic acid (ZDI = 0.0 ±0.00 mm), while susceptibility towards ampicillin and ciprofloxacin was intermediate. The isolate also exhibited γ -hemolytic activity and was identified as a Levilactobacillus brevis strain based on 16S rRNA gene sequencing. The isolate exhibited probiotic potential and was safe, affirming its potential application as a probiotic in the formulation of functional foods.

Levilactobacillus brevis, autochthonous to cucumber fermentation, is unable to utilize citric acid and encodes for a putative 1,2-propanediol utilization microcompartment.

The metabolic versatility of Levilactobacillus brevis, a heterofermentative lactic acid bacterium, could benefit environmentally compatible and low salt cucumber fermentation. The biodiversity of Lvb. brevis autochthonous to cucumber fermentation was studied using genotypic and phenotypic analyses to identify unique adjunct cultures. A group of 131 isolates autochthonous to industrial fermentations was screened using rep-PCR-(GTG)5 and a fermentation ability assay under varied combinations of salt (0 or 6%), initial pH (4.0 or 5.2), and temperature (15 or 30°C). No apparent similarities were observed among the seven and nine clusters in the genotypic and phenotypic dendrograms, respectively. A total of 14 isolates representing the observed biodiversity were subjected to comparative genome analysis. The autochthonous Lvb. brevis clustered apart from allochthonous isolates, as their genomes lack templates for citrate lyase, several putative hypothetical proteins, and some plasmid- and phage-associated proteins. Four and two representative autochthonous and allochthonous Lvb. brevis, respectively, were subjected to phenotype microarray analysis using an Omnilog. Growth of all Lvb. brevis strains was supported to various levels by glucose, fructose, gentiobiose, 1,2-propanediol, and propionic acid, whereas the allochthonous isolate ATCC14890 was unique in utilizing citric acid. All the Lvb. brevis genomes encode for 1,2-propanediol utilization microcompartments. This study identified a unique Lvb. brevis strain, autochthonous to cucumber, as a potential functional adjunct culture for commercial fermentation that is distinct in metabolic activities from allochthonous isolates of the same species.

The in vitro effects of probiotic bacteria on genital pathogens of female dogs

BackgroundAn important aspect in the microbiology of the reproductive system of small animals is the potential occurrence of probiotic bacteria, such as lactic acid bacteria (LAB) of the genus Lactobacillus. The presence of these microorganisms is significant due to their strong antibacterial and antifungal properties. This study aimed to select probiotic strains from the oral cavity and vagina that have outstanding antibacterial properties against typical genital pathogens of the female dog reproductive tract.ResultsThe antagonistic activity of ten LAB strains was tested against seven etiological agents isolated from the genital tract of female dogs with signs of inflammation. LAB strains with the greatest ability to inhibit the growth of indicator bacteria were Lactobacillus plantarum and L. acidophilus, while L. fermentum and L. brevis strains inhibited growth the least. Almost all strains showed a complete lack of adherence to Caco-2 epithelial cells.ConclusionsAll tested LAB isolates inhibited the in vitro growth of either Gram-positive or Gram-negative pathogens, suggesting that potential probiotic strains could contribute to the balance of the normal vaginal microbiota. Furthermore, they could be considered for use as prophylactic agents or as an alternative to antibiotic therapy for infections in dogs.

Isolation of γ-Aminobutyric Acid (GABA)-Producing Lactic Acid Bacteria with Anti-Inflammatory Effects from Fermented Foods in Korea

Lactic acid bacteria have become popular because of their γ-aminobutyric acid (GABA)-producing ability. In the present study, we selected four Levilactobacillus brevis strains (MG5552, MG5405, MG5261, and MG5522) with GABA-producing ability from the 33 strains isolated from various fermented foods in South Korea. We evaluated their GABA-producing ability using thin-layer chromatography and determined the GABA levels produced by each strain using an amino acid analyzer. Moreover, we investigated the anti-inflammatory activity of the selected strains, and the results revealed that the cell-free supernatant of the strains decreased nitric oxide (NO), inducible nitric oxide synthase (iNOS) expression, and nuclear factor kappa B (NF-κB) activity in RAW264.7 macrophages. Therefore, these GABA-producing LAB strains can regulate nerve excitement and act as probiotics with anti-inflammatory activity.