Plantarum Strains Research Articles

Biotransformation of camu-camu galloylated ellagitannins by Lactiplantibacillus plantarum with extracellular tannase activity.

Some strains of Lactiplantibacillus plantarum produce specific tannases that could enable the metabolism of ellagitannins into more bioavailable phenolic metabolites, thereby promoting the health effects of these polyphenols. However, the metabolic ability of these strains remains poorly understood. In this study, we analyzed the ability of broad esterase-producing (Est_1092+) and extracellular tannase-producing (TanA+) strains to convert a wide assortment of ellagitannins from camu-camu (Myrciaria dubia) fruit. To this end, forty-three strains were screened to identify and sequence (WGS) those producing Est_1092. In addition, six previously reported TanA+ strains were included in the study. Each strain (Est_1092+ or TanA+) was inoculated into a minimal culture medium supplemented with an aqueous camu-camu extract. After fermentation, supernatants were collected for semi-quantification of ellagitannins and their metabolites by mass spectrometry. For analysis, the strains were grouped according to their enzyme type and compared with an Est_1092 and TanA-lacking strain. Out of the forty-three isolates, three showed Est_1092 activity. Of the Est_1092+ and TanA+ strains, only the latter hydrolyzed the tri-galloyl-HHDP-glucose and various isomers of HHDP-galloyl-glucose, releasing HHDP-glucose and gallic acid. TanA+ strains also transformed three isomers of di-HHDP-galloyl-glucose, liberating di-HHDP-glucose and gallic acid. Overall, TanA+ strains released 3.6-4.9 times more gallic acid than the lacking strain. In addition, those exhibiting gallate decarboxylase activity pursued gallic acid metabolism to release pyrogallol. Neither Est_1092+ nor TanA+ strains transformed ellagitannin-core structures. In summary, TanA+ L. plantarum strains have the unique ability to hydrolyze a wide range of galloylated ellagitannins, releasing phenolic metabolites with additional health benefits.

Formation of the bacterial community as the basis of probiotic supplement for livestock

The paper presents the results of research on the creation of a community based on lactobacilli and bacilli with antimicrobial activity against pathogens of intestinal infections in farm animals. B. subtilis strain MP 2 and L. plantarum strain MP 5 included in the consortium are characterized by resistance to artificial gastric juice and bile salts, as well as the ability to form extracellular hydrolytic enzymes (xylanase, carboxymethylcellulase, avicelase, β-glucosidase, amylase, phytase, protease and lipase), antimicrobial (acids, bacteriocins, siderophores and exopolysaccharides) and antioxidant metabolites. B. subtilis strain MP 2 and L. plantarum strain MP 5 did not have hemolytic activity and did not carry genes responsible for toxin production, which indicates the potential safety of this bacteria. It was concluded that the developed consortium is promising for use as a probiotic for animal husbandry.

Evaluation of Sensory and Functional Compounds in Fermented Lactarius deliciosus Mushrooms

The effects of pretreatment and the addition of probiotic bacteria on the functional properties of fermented Lactarius deliciosus mushrooms were analyzed. Caps of L. deliciosus were blanched in water for 30 or 120 s (both at 96°C–98°C) or blanched in the microwave for 2 min (power 1000 W) as a pretreatment and fermented at 21°C and 26°C until pH ≤ 4.5 as a mark of successful fermentation. Lactobacillus acidophilus strain LA‐5 (Hansen) or Lactiplantibacillus plantarum strain SWA016 (Swanson) was added to the products to enrich the probiotic content. The type of pretreatment had a greater impact on the content of bioactive compounds in the products than fermentation temperature or the added probiotic bacteria. After fermentation, the pH of all products was below 4.5. Total dietary fiber (TDF) ranged from 45.74 ± 1.48 to 68.88 ± 2.84 g/100 g dm, and the highest content of TDF was observed in mushrooms blanched in water for 2 min. Beta‐glucans accounted for 30%–60% of TDF; mushrooms blanched in water for 30 s had the highest content of beta‐glucans (17.49 ± 0.46 to 30.38 ± 0.26 g/100 g dm) and phenolic compounds (1126.7 ± 52.2 to 1613.1 ± 40.4 mg/100 g dm), while microwave‐blanched mushrooms had the highest vitamin B1 (1.50 ± 0.08 to 2.78 ± 0.15 mg/100 g dm) and B2 (4.24 ± 0.38 to 7.58 ± 0.11 mg/100 g dm) contents. Water‐blanched mushrooms for 2 min scored the highest in the overall organoleptic analysis, and products with L. acidophilus strain LA‐5 (Hansen) were regarded as the most unfavorable. This study shows that fermented L. deliciosus exhibits nutraceutical properties and can be used in designing functional foods.

Extracellular vesicles from a novel Lactiplantibacillus plantarum strain suppress inflammation and promote M2 macrophage polarization.

Lactiplantibacillus plantarum (L. plantarum) is known for its probiotic properties, including antioxidant and anti-inflammatory effects. Recent studies have highlighted the role of extracellular vesicles (EVs) from prokaryotic cells in anti-inflammatory effects. This study aims to investigate the anti-inflammatory effects of extracellular vesicles derived from a newly isolated strain of L. plantarum (LP25 strain) and their role in macrophage polarization. The LP25 strain and its extracellular vesicles were isolated and identified through genomic sequencing, transmission electron microscopy (TEM), and nanoparticle tracking analysis (NTA). RAW 264.7 cells were treated with lipopolysaccharide (LPS) and/or LP25-derived extracellular vesicles (LEV). Morphological changes in the cells were observed, and the expression levels of pro-inflammatory cytokines (TNF-α, IL-6)、iNOS and anti-inflammatory cytokines (IL-10) 、Arg-1 were measured using quantitative real-time PCR (qPCR). Flow cytometry was used to detect the expression of Arg-1 in the treated cells. Treatment with LP25 EVs led to significant morphological changes in RAW 264.7 cells exposed to LPS. LP25 EVs treatment resulted in increased expression of Arg-1 and anti-inflammatory cytokines IL-10, and decreased expression of iNOS and surface markers protein CD86. Flow cytometry confirmed the increased expression of the M2 macrophage marker Arg-1 in the LP25 EVs-treated group. Extracellular vesicles from Lactiplantibacillus plantarum LP25 can suppress inflammatory responses and promote the polarization of macrophages toward the anti-inflammatory M2 phenotype. These findings provide new evidence supporting the anti-inflammatory activity of L. plantarum-derived EVs.

Both live and heat killed Lactiplantibacillus plantarum DPUL-F232 alleviate whey protein-induced food allergy by regulating cellular immunity and repairing the intestinal barrier.

Postbiotics have been proposed as clinically viable alternatives to probiotics, addressing limitations and safety concerns associated with probiotic use. However, direct comparisons between the functional differences and health benefits of probiotics and postbiotics remain scarce. This study compared directly the desensitization effect of probiotics and postbiotics derived from Lactiplantibacillus plantarum strain DPUL-F232 in the whey protein-induced allergic rat model. The results demonstrate that administering both live and heat killed F232 significantly alleviated allergy symptoms, reduced intestinal inflammation, and decreased serum antibody and histamine levels in rats. Both forms of F232 were effective in regulating the Th1/Th2 balance, promoting the secretion of the regulatory cytokine IL-10, inhibiting mast cell degranulation and restoring the integrity of the intestinal barrier through the upregulation of tight junction proteins. Considering the enhanced stability and reduced safety concerns of postbiotics compared to probiotics, alongside their ability to regulate allergic reactions, we suggest that postbiotics may serve as viable substitutes for probiotics in managing food allergies and potentially other diseases.

Selenium nanoparticles coated bacterial polysaccharide with potent antimicrobial and anti-lung cancer activities

Bacterial exopolysaccharides are homopolymeric or heteropolymeric polysaccharides with large molecular weights (10–1000 kDa). Exopolysaccharides' functional uses and potential have revolutionized the industrial and medicinal industries. Hence, the aim of the present study was to optimize the production of bacterial exopolysaccharide and apply it as a capping agent for selenium nanoparticles synthesis. Exopolysaccharide (EPS) producing Lactic acid bacteria (LAB) were isolated from dairy products then biochemically characterized and assessed for their potential antimicrobial effect. The most potent EPS producer was identified as Lactiplantibacillus plantarum strain A2 with accession number OP218384 using 16S rRNA sequencing. Overall, FTIR data of the extracted EPS revealed similarity with amylopectin spectrum. 1H NMR spectrum revealed an α-anomeric configuration of the glycosidic linkage pattern in the polysaccharides while the 13C NMR spectrum can also be separated into two main portions, the anomeric carbons region (δ 98–102 ppm) and the non-anomeric carbons region (δ 60–81 ppm). Antimicrobial activity of the produced EPS showed maximum activity against Staphylococcus aureus, MRSA, Enterobacter aerogenes, Klebsiella pneumoniae and Candida albicans respectively. The EPS capsule layer surrounding the bacterial cells was detected by TEM study. Optimization of EPS production was evaluated using Taguchi design, trial 23 reported the highest biomass yield and EPS output (6.5 and 27.12 g/L respectively) with 2.4 and 3.3 folds increase (from the basal media) respectively. The optimized exopolysaccharide was used as a capping and stabilizing agent for selenium nanoparticles (EPS-SeNPs) synthesis. Zeta potential, size and PDI of the synthesized nanoparticles were − 19.7 mV, 45–65 nm and 0.446 respectively with strong bactericidal and fungicidal effect against the tested pathogens. Complete microbial growth eradication was recorded after 6, 8 and 10 h against Staphylococcus aureus, Candida albicans and Klebsiella pneumoniae respectively. EPS-SeNPs showed a potent antioxidant effect reached 97.4% and anticancer effect against A549 lung cancer cell line (IC50 reached 5.324 µg/mL). EPS-SeNPs inhibited cancerous cell growth at S phase. Moreover, molecular studies revealed the anti-apoptotic activity of Bcl2's was inhibited and Bax was activated. The present investigation successfully synthesized selenium nanoparticles through bacterial EPS with significantly high antimicrobial and anticancer activity.

Complete genome sequence of Lactiplantibacillus plantarum strain GA_C_14 with potential characteristics applicable in the swine industry

Complete genome sequence of Lactiplantibacillus plantarum strain GA_C_14 with potential characteristics applicable in the swine industry

Distinct Microbial Taxa Are Associated with LDL-Cholesterol Reduction after 12 Weeks of Lactobacillus plantarum Intake in Mild Hypercholesterolemia: Results of a Randomized Controlled Study.

Probiotic microbes such as Lactobacillus may reduce serum total cholesterol (TC) and low-density lipoprotein (LDL) cholesterol. The objective of this study was to assess the effect of Lactobacillus plantarum strains CECT7527, CECT7528, and CECT7529 (LP) on the serum lipids, cardiovascular parameters, and fecal gut microbiota composition in patients with mild hypercholesterolemia. A randomized, double-blinded, placebo-controlled clinical trial with 86 healthy adult participants with untreated elevated LDL cholesterol ≥ 160mg/dl was conducted. Participants were randomly allocated to either placebo or LP (1.2 × 109CFU/d) for 12weeks. LDL, HDL, TC, and triglycerides (TG), cardiovascular parameters (blood pressure, arterial stiffness), and fecal gut microbiota composition (16S rRNA gene sequencing) were assessed at baseline and after 12weeks. Both groups were comparable regarding age, sex, and LDL-C at baseline. LDL-C decreased (mean decrease - 6.6mg/dl ± - 14.0mg/dl, Ptime*group = 0.006) in the LP group but not in the placebo group. No effects were observed on HDL, TG, or cardiovascular parameters or overall gut microbiota composition. Responders to LP intervention (> 5% LDL-C reduction) were characterized by higher BMI, pronounced TC reduction, higher abundance of fecal Roseburia, and lower abundance of Oscillibacter. In conclusion, 12weeks of L. plantarum intake moderately reduced LDL-C and TC as compared to placebo. LDL-C-lowering efficacy of L. plantarum strains may potentially be dependent on individual difference in the gut microbiota. Trial registration: DRKS00020384, dated 07/01/2020.

Production and characterization of plantaricin Y11 from <i>Lactiplantibacillus Plantarum</i> strain y11 (MW642245.1) isolated from Nigerian food samples and their applications in preserving milk

Bacteriocin from lactic acid bacterium (LAB) was characterized and its biopreservation assay carried out using conventional methods and integrative approaches. About 66.7% (n=180) of the bacterial strains isolated from twelve different fermented/non-fermented food products were potential LAB strains by biochemical characterization. The highest bacteriocin producing strain was selected and confirmed with 16S rRNA sequencing and submitted to GenBank of National Center for Biotechnology Information as Lactiplantibacillus plantarum strain Y11 (Accession number: MW642245.1). Polymerase Chain Reaction (PCR) revealed the presence of virulence genes (cytotoxin K and haemolysin C) in L. plantarum Y11. The bacteriocin produced was labelled as plantaricin Y11 with molecular weight of 1540 Da, amino acid sequence was NSHGTADYCVMWLIXK, and possessed the merits of wide pH stability (2–10), high thermal stability and sensitivity to protease. The bacteriocin showed wide spectrum of activity against bacterial reference strains with bacteriocin activity ranging from 3200Au/mL to 6400Au/mL. Preservative potentials of the bacteriocin compared favourably with sodium benzoate in milk, inhibiting bacterial and fungal load compared to the control. There was log reduction of aerobic mesophilic bacterial count of 8.02±0.15 and 8.43±0.21 Log 10 CFU/mL in milk treated with plantaricin Y11 and sodium benzoate, respectively. The log reductions of fungal count in plantaricin Y11 and sodium benzoate treated milk ≥4.41±0.11 and ≥3.1±0.2 Log 10 CFU/mL respectively. The plantaricin Y11 was then classified as class IIa in bacteriocin classification schemes and it sustained some organoleptic conditions of milk making it a promising candidate for safe bio-preservatives.

Carbohydrate-active enzyme profiles of Lactiplantibacillus plantarum strain 84-3 contribute to flavor formation in fermented dairy and vegetable products

Microbes are critical for flavor formation in fermented foods; however, their mechanisms of action are not fully understood. The microbial composition of 51 dairy and 47 vegetable products was functionally annotated and the carbohydrate-active enzyme (CAZyme) profiles of Lactiplantibacillus plantarum 84-3 (Lp84-3), isolated from dairy samples, can promote resistant starch (RS) degradation, were analyzed. Lactobacillus, Streptococcus, and Lactococcus were the predominant genera in dairy products, whereas the major genera in vegetables were Lactobacillus, Weissella, and Carnimonas. Phages from Siphoviridae, Myoviridae, and Herelleviridae were also present in dairy products. Additionally, the glycosyl hydrolase (GHs) family members GH1 and GH13 and the glycosyltransferase (GTs) family members GT2 and GT4 were abundant in Lp84-3. Moreover, Lp84-3 was enriched in butanoate metabolism enzymes and butanoate metabolite compounds. Therefore, fermented food microbes, especially Lp84-3, have an abundant repertoire of enzymes that promote flavor production, as starter improving the flavor of fermented dairy and vegetable products.

From Traditional Dairy Product "Katak" to Beneficial Lactiplantibacillus plantarum Strains.

Traditional milk products, widely consumed in many countries for centuries, have been drawing renewed attention in recent years as sources of bacteria with possible bioprotective properties. One such product for which only limited information exists is the traditional Bulgarian "katak". This fermented yogurt-like product, renowned for its taste and long-lasting properties, possesses specific sensory characteristics. In this study, 18 lactic acid bacteria (LABs) were isolated from artisanal samples made in the Northwest part of Bulgaria. A polyphasic taxonomic approach combining classical phenotypic and molecular taxonomic methods, such as multiplex PCR, 16S rDNA sequencing, and MALDI-TOF MS, was applied, leading to the identification of 13 strains. The dominance of Lactiplantibacillus plantarum was confirmed. In vitro tests with the identified strains in model systems showed a promising broad strain-specific spectrum of activity against food-borne and human pathogens (Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli). Non-purified Lactobacillus postbiotics, produced during fermentation in skimmed and soya milks and in MRS broth, were estimated as limiting agents of virulence factors. The LAB's production of lactate, acetate, and butyrate is a promising probiotic feature. A further characterization of the active strains and analysis of the purified post-metabolites are needed and are still in progress.

Effects of mixed starters of plant- and wine-derived L. plantarum on hawthorn juice fermentation: Physicochemical properties, phenolic and volatile profiles

Lactic acid bacteria (LAB) fermentation is an effective way to improve the nutrition and sensory qualities of hawthorn juice, however the scarcity of LAB strains adapting to the high acidity of hawthorn juice limits its industrial application. In this study, a total of thirty-seven LAB strains belonging to different genera and species were isolated from spontaneously fermented plant and spine grape wine products, and four acid-resistant L. plantarum strains (Lpl.58, Lpl.55, Lpl.69 and Lpl.HY-1) were finally screened according to their viability and fermentation activity in hawthorn juice. The influences of their single and dual-mixed inoculation on the physicochemical properties, antioxidant activity, phenolic compounds and volatile flavor compounds of hawthorn probiotic beverages were subsequently investigated. Compared to single fermentation, mixed fermentation achieved higher fermentation activity, cell viability, and acid production, especially Lpl.69 + Lpl.HY-1, which also exhibited the greatest antioxidant activity. A significant increase of phenolic compounds (e.g. chlorogenic acid, proanthocyanidin B1, proanthocyanidin B2) was observed in Lpl.58 + Lpl.HY-1. Notably, co-inoculating Lpl.69 + Lpl.HY-1 and Lpl.55 + Lpl.HY-1 largely reduced volatile compounds with unpleasant odor (hexanol and hexanal), and increased the levels of desired aroma compounds (alcohols, esters, aldehydes and ketones) compared to single fermentation. The obtained results of this study indicated that screening L. plantarum strains from different acidic matrices and conducting mixed fermentation was a promising approach to produce hawthorn probiotic beverages with high nutrition and aroma complexity.

Selection of Lactiplantibacillus plantarum strains as inoculant of rice straw fermentation and its fermentation characteristics

Selection of Lactiplantibacillus plantarum strains as inoculant of rice straw fermentation and its fermentation characteristics

Selection of Lactiplantibacillus plantarum strains as inoculant of rice straw fermentation and its fermentation characteristics

Selection of Lactiplantibacillus plantarum strains as inoculant of rice straw fermentation and its fermentation characteristics

Multi-species endophytic Bacillus for improved control of potato soilborne and tuber-borne diseases in Tunisia: from laboratory to field conditions

BackgroundDue to the soilborne and tuber-borne nature of their causative agents, Fusarium wilt, Rhizoctonia root canker and black dot diseases are still leading to serious problems in potato production in Tunisia and worldwide. Among endophytic bacteria, the genus Bacillus is one of the most exploited microbial groups known as potent biocontrol agents against several potato diseases. In the present study, six strains belonging to five Bacillus species were screened for their abilities to inhibit root and wilt potato pathogens in vitro, in vivo and under natural conditions over three cropping seasons and to promote plant growth.ResultsBased on the dual-culture assays, the whole-cell suspensions of SV39 and SV104 (Bacillus tequilensis), SV41 (B. subtilis), SV44 (B. methylotrophicus) and SV65 (B. amyloliquefaciens subsp. plantarum) strains exhibited potent antifungal activity against important potato soilborne phytopathogens with ~ 65 to 70% inhibition rates. Significant inhibition rates were also induced by the cell-free culture filtrates, the butanolic and the chloroformic extracts depending on the target pathogens, the concentration used and the Bacillus strain tested. In pot experiment, a decrease in Rhizoctonia root canker severity, ranging from 43 to 65% compared to the inoculated and untreated control, was induced by all Bacillus spp. strain-based treatments, while SV39-, S42- and SV65-based treatments were the most effective in suppressing by 50–53 and 65–52%, black dot severity and the relative vascular discoloration extent induced by F. oxysporum f. sp. tuberosi, respectively, relative to positive control. This biocontrol potential was associated with an enhancement of potato growth parameters. Field studies indicated that soil treatment with the most of the Bacillus spp. strains had significantly controlled all the target fungal soilborne diseases and improved at the least two growth and/or production parameters depending on the strain used and the cropping seasons. SV39-, SV41-, SV44- and SV104-based treatments resulted in a significant increase in tuber yield in one cropping season.ConclusionThese Bacillus spp. strains could be used in combinations and/or introduced with other existing practices in order to provide supplemental control of target diseases and yield promotion under organic or conventional potato production systems.

Sediment bioelectrochemical system with potential application against vibriosis in aquaculture

Aquaculture can suffer from heavy losses caused by vibriosis, which denotes diseases caused by Vibrio bacteria. Due to disadvantages of available measures, mostly involving the use of antibiotics, to control these bacteria, novel measures are still needed. Therefore, aiming at an innovative solution for that issue in a long term, we investigated the inhibitory effects of the sediment bioelectrochemical system (SBES) on a V. harveyi strain (Vh) and a V. parahaemolyticus strain (Vp). SBESs were installed in test pond models that were lab-scale plastic tanks containing artificial brackish water, while the resembling systems not having SBESs were used as the controls. Once the SBES stably generated electricity (at ca. 0.5 mA), the tests with the Vibrio strains were conducted by: (i) supplementing the Vibrio cell suspensions directly into the tank waters, (ii) immersing the Vibrio cells suspensions each in an isolated axenic space into the tank environments, and (iii) adding the filtered tank waters after taken out of the tanks to the Vibrio cells. Based on plate enumeration to evaluate the inhibitory effects of such treatments on the Vibrio strains, we discovered that almost 100% of both Vh and Vp cells could not grow after 5 min in contact with the SBES water while more than 80% of them could still grow after 1–2 h in contact with the water from the control tanks. Paralleling tests showed that the SBES water was also toxic to an Escherichia coli strain but only slightly inhibited a Bacillus pumilus strain and a Lactobacillus plantarum strain, reducing their growths by only about 60% and 30%, respectively. Further tests revealed that the effects were not due to suspected proteinacous components or metal contents or peroxides in the SBES water. On the other hand, applying a redox potential of 20 mV (vs. Ag/AgCl), which was the anode potential measured in the SBES, onto a graphite rod immersed in Vh cell suspension led to the growth inhibition to 90% of the cells, although the unpoised graphite rod also seemed toxic, inhibiting ca. 60% of Vh cells. A similar experiment with titanium (known to be non-toxic to bacteria), instead of graphite, clearly showed the vibrio-inhibiting effect of the applied redox potential. Altogether, the results directly evidence the inhibitory effect of the SBES on V. harveyi and V. parahaemolyticus. This effect, together with the mild effect on the beneficial bacilli, implies that SBES integration in aquaculture ponds can be a promising novel technological option that allow controlling vibriosis in-situ while minimizing the uses of antibiotics or other chemicals, toward more sustainable aquaculture practices.

Isolation of Lactic Acid Bacteria (LAB) from Mimosa pudica (Semalu) for Production of Bacterial Cellulose

Bacterial cellulose (BC) is a potential eco-friendly biopolymer. BC has higher crystallinity and purity compared to plant cellulose. Scientific studies on the production of BC from lactic acid bacteria (LAB) are minimal compared to other common bacteria such as Acetobacter xylinum. LAB was screened and isolated from different tissues of Mimosa pudica (medicinal plant) using MRS broth and agar as the selective medium. LAB isolates were subjected to 16S rRNA gene sequencing of all the bacterial isolates. BC was produced from all LAB isolates by incubating at 30 °C for 14 days in herbal tea medium (Strobilanthes crispus) and HS medium (control) with 130 r.p.m agitation. BC produced by two selected bacterial isolates was characterized using FESEM, FTIR, XRD, and TGA. Molecular analysis of the 16S rRNA gene of all the potential LAB isolates shows 99.86 - 100% identity to 16S rRNA sequences of other Lactobacillus plantarum strains. Two selected L. plantarum strains (LBM001 & LBM004) produce BC in sphere-like particles with a 1.4 to 2.2 µm diameter range of microfiber. FTIR analysis shows that BC produced by LBM001 and LBM004 have four similar cellulose regions identified in cellulose from other sources, which are O-H stretch (3400-330 cm-1), C-H stretch (2970-2800 cm-1), O-H bending (1620cm-1) and C-O-C stretch (1100-1073 cm-1). XRD analysis shows BC produced by the L. plantarum strains consists of two different XRD peaks at the 2θ angle of 21.53° and 21.85° instead of a single peak (22.76°) identified in the BC produced by A. xylinum and plant cellulose. A similar TG and DTG curved pattern was detected in the BC produced by the L. plantarum strains with the BC produced by A. xylinum and plant cellulose. The LAB isolates from M. pudica have potential in BC production based on the multiple characterization studies.

Lactiplantibacillus plantarum from Unexplored Tunisian Ecological Niches: Antimicrobial Potential, Probiotic and Food Applications.

The continued exploration of the diversity of lactic acid bacteria in little-studied ecological niches represents a fundamental activity to understand the diffusion and biotechnological significance of this heterogeneous class of prokaryotes. In this study, Lactiplantibacillus plantarum (Lpb. plantarum) strains were isolated from Tunisian vegetable sources, including fermented olive and fermented pepper, and from dead locust intestines, which were subsequently evaluated for their antimicrobial activity against foodborne pathogenic bacteria, including Escherichia coli O157:H7 CECT 4267 and Listeria monocytogenes CECT 4031, as well as against some fungi, including Penicillium expansum, Aspergilus niger, and Botrytis cinerea. In addition, their resistance to oro-gastro-intestinal transit, aggregation capabilities, biofilm production capacity, adhesion to human enterocyte-like cells, and cytotoxicity to colorectal adenocarcinoma cell line were determined. Further, adhesion to tomatoes and the biocontrol potential of this model food matrix were analyzed. It was found that all the strains were able to inhibit the indicator growth, mostly through organic acid production. Furthermore, these strains showed promising probiotic traits, including in vitro tolerance to oro-gastrointestinal conditions, and adhesion to abiotic surfaces and Caco-2 cells. Moreover, all tested Lpb. plantarum strains were able to adhere to tomatoes with similar rates (4.0-6.0 LogCFU/g tomato). The co-culture of LAB strains with pathogens on tomatoes showed that Lpb. plantarum could be a good candidate to control pathogen growth. Nonetheless, further studies are needed to guarantee their use as probiotic strains for biocontrol on food matrices.

Characterizing the impact of species/strain-specific Lactiplantibacillus plantarum with community assembly and metabolic regulation in pickled Suancai

To investigate the colonization and impact of the specific Lactiplantibacillus plantarum strains, four isolated strains were applied in pickled Suancai which is a traditional pickled mustard (Brassica juncea). Results showed that strain-8 with the highest lactic acid bacteria (LAB) counts and acetic acid (p < 0.05). There were 11.42 % ∼ 32.35 % differential volatile compounds detected, although nitriles, esters, and acids were predominant. L. plantarum disturbed the microbial community, in which the microbial composition of strain-11 was most similar to the naturally fermented sample. Amino acids, carbohydrate metabolism, and metabolism of cofactors and vitamins were the main functional classes because of the similar dominant microbes (Lactiplantibacillus and Levilactobacillus). The functional units were separated based on NMDS analysis, in which bacterial chemotaxis, amino acid-related units, biotin metabolism, fatty acid biosynthesis, and citrate cycle were significantly different calculated by metagenomeSeq and Benjamin-Hochberg methods (p < 0.05). The contents of most flavor compounds were consistent with their corresponding enzymes. In particular, glucosinolates metabolites were different and significantly related to the myrosinase and metabolic preference of LAB. Therefore, this study revealed the impact mechanism of the specific L. plantarum strains and provided a perspective for developing microbial resources to improve the flavor diversity of fermented vegetables.

Lactiplantibacillus plantarum strains with proteolytic abilities showed diverse effects on casein gel formation during fermentation

Proteolysis is often used to improve gel-forming properties of protein, however, the proteolytic effect of lactic acid bacteria on protein gel properties has been rarely reported. The purpose of this study is to investigate the potential role of proteolysis by Lactiplantibacillus plantarum in casein gel formation during fermentation. A total of fifty-four L. plantarum strains were subjected to a screening of proteolytic ability and twenty-one strains were found possessing extracellular protease-producing abilities. The top nine strains with varying proteolytic abilities were investigated for their impacts on casein gel formation. Interestingly, the casein gels fermented by the strains with the highest and lowest proteolytic abilities both showed relatively low hardness and lower storage modulus (G′) and loss modulus (G″) in rheological analyses. However, two strains, namely L. Plantarum YM13-8.1 and L. Plantarum YN22-3.1, which possess a relatively moderate level of proteolytic ability among the nine strains, significantly improved the hardness and water-holding capacity of casein gels and presented a more dense and uniform gel structure, which was accompanied by an increased hydrophobicity and disulfide bond content. The results indicate that the strains YM13-8.1 and YN22-3.1 can facilitate the formation of casein gel by improving the aggregation of protein molecules in fermentation. Concludingly, we propose that the proteolysis by L. plantarum proteinases dramatically influences the casein gel properties, and the effects, to a certain degree, are strain-specific.