Exopolysaccharide Produced by Plant-Derived Lactobacillus plantarum SN35N Exhibits Antiviral Activity.

A lactic acid bacterial strain, Lactobacillus plantarum SN35N, which has been isolated from the pear, secretes negatively charged acidic exopolysaccharide (EPS) to outside cells. We have previously found that the SN35N-derived acidic EPS inhibits the catalytic activity of hyaluronidase (EC 3.2.1.35) promoting inflammation. The aim of this study is to find other health benefits of EPS. EPS has been found to exhibit an inhibitory effect against the influenza virus (Alphainfluenzavirus Influenza A virus) and feline calicivirus (Vesivirus Feline calicivirus), which is recognized as a model of norovirus. Although more studies on the structure-function relationship of EPSs are needed, SN35N-derived EPS is a promising lead for developing not only anti-inflammatory agents, but also antiviral substances.

Genotypic and phenotypic diversity among Lactobacillus plantarum and Lactobacillus pentosus isolated from industrial scale cucumber fermentations.

The Lactobacillus plantarum and Lactobacillus pentosus genotypes existing in industrial-scale cucumber fermentations were defined using rep-PCR-(GTG)5. The ability of each genotype to ferment cucumbers under various conditions was evaluated. Rep-PCR-(GTG)5 was the technique capable of illustrating the most intraspecies discrimination compared to the sequencing of housekeeping genes (recA, dnaK, pheS and rpoA), MLST and RAPD with primers LP1, OPL5, M14 and COC. Ten genotypic clusters were defined for the 199 L. pentosus tested and three for the 17 L. plantarum clones. The ability of the 216 clones genotyped and 37 additional cucumber fermentation isolates, of the same species, to rapidly decrease the pH of cucumber juice medium under various combinations of sodium chloride (0 or 6%), initial pH (4.0 or 5.2) and temperatures (15 or 30 °C) was determined using a fractional factorial screening design. A reduced fermentation ability was observed for the L. plantarum strains as compared to L. pentosus, except for clone 3.2.8, which had a ropy phenotype and aligned to genotypic cluster A. L. pentosus strains belonging to three genotypic clusters (B, D and J) were more efficient in cucumber juice fermentation as compared to most L. plantarum strains. This research identified three genetically diverse L. pentosus strains and one L. plantarum as candidates for starter cultures for commercial cucumber fermentations.

Lactobacillus plantarum ATG-K2 and ATG-K6 Ameliorates High-Fat with High-Fructose Induced Intestinal Inflammation.

Obesity has become a worldwide health problem, and many significant inflammatory markers have been associated with the risk of side effects of obesity and obesity-related diseases. After a normal diet or high-fat diet with high-fructose water (HFHF) for 8 weeks, male Wistar rats were divided randomly into four experimental groups according to body weight. Next, for 8 weeks, a normal diet, HFHF diet, and HFHF diet with L. plantarum strains ATG-K2 or ATG-K6 were administered orally. Compared to the control group, the HFHF diet group showed significantly increased visceral fat, epididymal fat, and liver weight. The mRNA and protein expression levels of FAS and SREBP-1c were higher in the HFHF diet group than in the HFHF diet with L. plantarum strains ATG-K2 and ATG-K6. The HFHF diet with L. plantarum strain ATG-K2 showed significantly decreased inflammatory cytokine expression in the serum and small intestine compared to the HFHF diet group. Furthermore, histological morphology showed minor cell injury, less severe infiltration, and longer villi height in the small intestine ileum of the HFHF diet with L. plantarum strains groups than in the HFHF diet group. These results suggest that L. plantarum strains K2 and K6 may help reduce intestinal inflammation and could be used as treatment alternatives for intestinal inflammatory reactions and obesity.

Comparative proteomic analysis of three Lactobacillus plantarum strains under salt stress by iTRAQ.

BACKGROUND: Lactobacillus plantarum, a common species of lactic acid bacteria, is used to improve the flavor of traditional fermented food. Under salt stress, different strains of L. plantarum can respond differently. In this work, proteomics and bioinformatics analysis of L. plantarum strains (ATCC14917, FS5-5, and 208) grown under salt stress (240 g L-1 sodium chloride (NaCl)) were investigated based on the isobaric tags for relative and absolute quantitation method. RESULTS: Although 171 differentially expressed proteins (DEPs) were observed, only 44, 57, and 112 DEPs were identified in the strains ATCC14917, FS5-5, and 208 respectively. There were 33, 191, and 179 specific DEPs in ATCC14917 versus FS5-5, in 208 versus FS5-5, and in strain 208 versus ATCC14917 in 240 g L-1 NaCl. These DEPs indicate that the three strains, from pickles, fermented soybean paste, and fermented milk, may have different salt stress responses. Gene Ontology enrichment and Kyoto Encyclopedia of Genes and Genomes analysis showed that most DEPs observed were involved in protein biosynthesis, nucleotide metabolism, and sugar metabolism. Twenty-six significantly different DEPs that were possibly associated with salt response were selected and further analyzed for gene expression level and pattern by quantitative reverse transcription polymerase chain reaction. Pyruvate kinase and cysteine desulfurase had similar expression patterns in all three strains; glutamate decarboxylase expression was upregulated in FS5-5 and significantly upregulated in strain 208; RNA polymerase subunit alpha was downregulated in FS5-5 but upregulated in strain 208. CONCLUSIONS: These results also showed that the salt stress response of strain 208 may involve higher numbers of genes than the other strains. This research provides a theoretical basis for improvement of salt tolerance of L. plantarum in industrial production. © 2020 Society of Chemical Industry.

A Method of Direct Quantitation of Lactobacillus spp. in Intestinal Contents Based on Real-Time PCR.

The method of direct quantitation of Lactobacillus spp. and L. acidophilus in intestinal contents based on real-time PCR was developed. It does not require culturing and allows estimating the number of living lactobacilli cells (measured in lg CFU) in absolute quantitative PCR format.

Proposal of Lactobacillus kosoi Chiou et al. 2018 as a later heterotypic synonym of Lactobacillus micheneri McFrederick et al. 2018, elevation of Lactobacillus plantarum subsp. argentoratensis to the species level as Lactobacillus argentoratensis sp. nov., and Lactobacillus zhaodongensis sp. nov., isolated from traditional Chinese pickle and the intestinal tract of a honey bee (Apis mellifera).

Lactobacillus kosoi Chiou et al. 2018 and Lactobacillus micheneri McFrederick et al. 2018 are closely related, and they share 100 % 16S rRNA gene sequence similarity, 99.6 % pheS gene sequence similarity, 100 % rpoA gene sequence similarity, 97.3 % average nucleotide identity (ANI) value and 76.6 % in silico DNA-DNA hybridization (isDDH) value, indicating that they represent the same species. Fatty acid methyl esters (FAME) analysis and phenotypic characterization also indicated that L. kosoi and L. micheneri are very similar. We propose L. kosoi Chiou et al. 2018 as a later heterotypic synonym of L. micheneri McFrederick et al. 2018. The taxonomic position of Lactobacillus plantarum subsp. argentoratensis in the L. plantarum group was re-examined using a polyphasic approach, including sequence analyses of 16S rRNA, pheS, rpoA and recA genes, average nucleotide identity analysis, in silico DNA-DNA hybridization, fatty acid methyl ester analysis and phenotypic characterization. Results of 16S rRNA gene sequence analysis indicated that L. plantarum subsp. argentoratensis was closely related to L. plantarum subsp. plantarum, L. pentosus and L. paraplantarum in the L. plantarum group, sharing 99.6-99.7 % 16S rRNA gene sequence similarities. Results of pheS, rpoA and recA gene sequence analyses indicated that L. plantarum subsp. argentoratensis was most closely related to L. plantarum subsp. plantarum, having 91.8 % pheS gene sequence similarity, 98.9 % rpoA gene sequence similarity and 93.1 % recA gene sequence similarity. L. plantarum subsp. argentoratensis DSM 16365T shared 95.6 % ANI value and 62.9 % isDDH value with L. plantarum subsp. plantarum ATCC 14917T. The low isDDH value confirmed that L. plantarum subsp. argentoratensis and L. plantarum subsp. plantarum represent two different species, rather than two different subspecies in the L. plantarum group. On the basis of the data from polyphasic characterization obtained in the present study and in previous studies, L. plantarum subsp. argentoratensis is elevated to the species level and represents a novel species of the genus Lactobacillus, for which the name Lactobacillus argentoratensis sp. nov. is proposed and the type strain is DKO 22T (=CIP 108320T=DSM 16365T=JCM 16169T). Two novel Gram-stain-positive bacterial strains, designated 1206-1T and F027-1-2, were isolated from traditional pickle in Heilongjiang Province, PR China, and from the intestinal tract of a honey bee (Apis mellifera) in Hubei Province, PR China, respectively. The two bacteria were characterized by a polyphasic approach, including 16S rRNA gene sequence analysis, pheS gene sequence analysis, rpoA gene sequence analysis, fatty acid methyl ester analysis, average nucleotide identity analysis, in silico DNA-DNA hybridization analysis and an analysis of phenotypic features. The results of 16S rRNA gene sequence analysis indicated that strains 1206-1T and F027-1-2 were distantly related to Lactobacillus sharpeae, Lactobacillus hulanensis, Lactobacillus songhuajiangensis, Lactobacillus pantheris, Lactobacillus thailandensis, Lactobacillus camelliae, Lactobacillus jixianensis, Lactobacillus nasuensis, Lactobacillus baoqingensis, Lactobacillus manihotivorans and Lactobacillus porcinae. Strain 1206-1T exhibited 94.2-96.4 % 16S rRNA gene sequence similarities, 69.5-83.3 % pheS gene sequence similarities and 73.1-90.3 % rpoA gene sequence similarities to type strains of phylogenetically related species. ANI and isDDH values between strain 1206-1T and the type strains of phylogenetically related species were 52.7-73.7 % and 21.1-30.1 %, respectively. On the basis of the data obtained in the present study, a novel species, Lactobacillus zhaodongensis sp. nov. is proposed and the type strain is 1206-1T (=CCM 8981T=CCTCC AB 2019200T=LMG 31620T).

The status of the species Lactobacillus fornicalis Dicks et al. 2000. Request for an opinion.

During a recent study on members of the genus Lactobacillus we realized that cultures of Lactobacillus fornicalis TV 1018T (=DSM 13171T=ATCC 700934T) are no longer available from the online catalogue of the German Collection of Microorganisms and Cell Cultures GmbH, being displayed as Lactobacillus plantarum at the American Type Culture Collection. Based on data currently available, the organism deposited as ATCC 700934T is a member of the species Lactobacillus plantarum subs. plantarum. Therefore, the type strain of Lactobacillus fornicalis cannot be included in any further scientific comparative study. This matter is referred to the Judicial Commission, asking for an opinion on the status of the species.

Fermentation with mono- and mixed cultures of Lactobacillus plantarum and L. casei enhances the phytochemical content and biological activities of cherry silverberry (Elaeagnus multiflora Thunb.) fruit.

BACKGROUND: Lactic acid fermentation has been widely used to improve the nutritional and functional properties of food products. Cherry silverberry (Elaeagnus multiflora Thunb.) is considered as an invasive plant species with known medicinal and functional properties. In this study, improvement of the biological activity and health benefits of cherry silverberry fruit through lactic acid fermentation was investigated. RESULTS: Extracts of cherry silverberry fruits fermented by pure cultures of Lactobacillus plantarum KCTC 33131 and L. casei KCTC 13086 exhibited favorable physicochemical properties and enhanced phytochemical content, antioxidant properties (DPPH radical scavenging activity, reducing power, superoxide dismutase-like property and hydrogen peroxide scavenging activity) and α-glucosidase and tyrosinase enzyme inhibitory activity as compared with unfermented fruits. Despite a decrease in the specific phenolic acid contents among the fermented samples, the cherry silverberry fruit fermented by mixed cultures of L. plantarum and L. casei contained superior total polyphenols (3.78 ± 0.22 mg GAE g-1 ) and total (0.66 ± 0.12 mg QE g-1 ) and individual flavonoid contents in comparison with fruits fermented by single cultures and unfermented ones. Multivariate analysis also showed strong association among total phytochemical contents and biological activities. CONCLUSIONS: This work has elucidated the effect of fermentation with L. plantarum KCTC 33131 and L. casei KCTC 13086 on the improvement of the physicochemical properties and biological activity of cherry silverberry fruit. It also revealed the potential application of fermented cherry silverberry in the production of food materials beneficial for health. © 2020 Society of Chemical Industry.

Inhibition of Escherichia coli adhesion to human intestinal Caco-2 cells by probiotic candidate Lactobacillus plantarum strain L15.

Probiotics are microbial strains beneficial to human health if consumed in appropriate amounts. Their potential has recently led to a significant increase in research interest in their effects on the intestine, mainly by reinforcing the intestinal epithelium and modulating the gut microbiota. This study aimed to evaluate the probiotic features of Lactobacillus plantarum strain L15 based on adhesive properties for the inhibition of the adhesion of infectious pathogens. The molecular identification of the strain was performed from the sequencing of 16S ribosomal DNA with 27FYM and 1492R primers, and its probiotic features, including resistance to gastric juices, resistance to bile salts, and hydrophobicity were evaluated. The potential of Lactobacillus plantarum strain L15 to adhere to human adenocarcinoma intestinal cell line, Caco-2, as well as the auto and co-aggregation and anti-adherence activity against Escherichia coli were investigated. The results demonstrated that this strain has a desirable potential for passing through the low pH of the stomach and entering the intestines. Moreover, 54% hydrophobicity, 44% auto-aggregation, and 32% co-aggregation were observed for this strain. The adhesion level of Lactobacillus plantarum strain L15 to Caco-2 cells was 12%, and adhered lactobacilli cells were observed by scanning electron microscopy (SEM). Furthermore, this strain showed appropriate anti-adherence effects, including competition, inhibition, and replacement properties against Escherichia coli. The results indicated that Lactobacillus plantarum strain L15 had good potential for exerting antagonistic effects against E. coli.

Draft genome sequence of Lactobacillus plantarum C4 (CECT 9567), a potential probiotic strain isolated from kefir.

Lactobacillus plantarum C4 (CECT 9567) was isolated from kefir and has been extensively studied because of its probiotic properties. Here we report the genome sequence of this strain. The genome consists of 3,221,350 bp, and contains 3058 CDSs with an average G + C content of 44.5%. The genome harbors genes encoding the AraC-family transcription regulator, the penicillin-binding protein Pbp2A, and the Na+/H+ antiporter NapA3, which have important roles in the survival of lactobacilli in the gastrointestinal tract. Also, the genome encodes the catalase KatE, NADH peroxidase and glutathione peroxidase, which enable anaerobic respiration, and a nitrate reductase complex, which enable anaerobic respiration. Additionally, genes encoding plantaricins and sactipeptides, and genes involved in the use of fructooligosaccharides and in the production of butyric acid were also identified. BLASTn analysis revealed that 91.4% of CDSs in C4 genome aligned with those of the reference strain L. plantarum WCFS1, with a mean identity of 98.96%. The genome information of L. plantarum C4 provides the basis for understanding the probiotic properties of C4 and to consider its use as a potential component of functional foods.

In vitro and in vivo investigations of probiotic properties of lactic acid bacteria isolated from Chinese traditional sourdough.

A total of 88 lactic acid bacteria (LAB) strains were isolated from Chinese traditional sourdough and five of them were selected based on their bile resistance. All the five strains were identified as Lactobacillus plantarum by 16S rRNA gene sequencing. In vitro probiotic properties of the L. plantarum strains including tolerance to simulated gastrointestinal conditions, aggregation activity, and cholesterol removal ability were assessed. Two representatives, L. plantarum ZJUFT34 and L. plantarum ZJUFT17, were intragastrically administered to male C57BL/6J mice of 4-week age for 6 weeks to evaluate their in vivo health-promoting effects. The results indicated that L. plantarum ZJUFT34, L. plantarum ZJUFHN9, and L. plantarum ZJUFAH5 could survive the 3-h incubation in simulated gastric juice with a pH value of 2.0, while L. plantarum ZJUFT32 and L. plantarum ZJUFT17 exhibited better autoaggregation activities and coaggregation activities with pathogens. All the strains showed a cholesterol removal ability in vitro. However, L. plantarum ZJUFT34 or L. plantarum ZJUFT17 administration did not significantly change the serum total cholesterol in vivo. But the ratio of high-density lipoprotein cholesterol to low-density lipoprotein cholesterol was significantly increased by the L. plantarum administration. Besides, L. plantarum ZJUFT17 significantly lowered serum tumor necrosis factor (TNF)-α concentrations. Furthermore, the administration of the LAB strains showed significant influences on lipid metabolism-related gut microbiota. These findings suggested that the L. plantarum strains may benefit the prevention of metabolic syndrome.

Preventive effect of Lactobacillus plantarum KSFY02 isolated from naturally fermented yogurt from Xinjiang, China, on d-galactose-induced oxidative aging in mice.

Yogurt from Xinjiang, China, is a traditional and naturally fermented food, and abundant microorganisms are produced during its fermentation process. In this study, we carried out in vivo animal experiments to explore the effect of a newly isolated lactic acid bacterial strain, Lactobacillus plantarum KSFY02 (LP-KSFY02), on oxidative aging. We used d-galactose to induce oxidative aging in mice and analyzed the serum and tissues of those mice using molecular biology detection methods. The results showed that LP-KSFY02 could inhibit the decreases in the thymic, cerebral, cardiac, liver, spleen, and kidney indices of mice caused by oxidative aging. The LP-KSFY02 strain increased activity of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and glutathione (GSH) and reduced levels of nitric oxide (NO) and malondialdehyde in the serum, liver, and spleen of the oxidative aging mice. Pathological observation demonstrated that LP-KSFY02 alleviated damage to the liver and spleen of oxidative aging mice. Quantitative PCR showed that LP-KSFY02 effectively upregulated mRNA expression of neuronal nitric oxide synthase (Nos1), endothelial nitric oxide synthase (Nos3), copper/zinc superoxide dismutase (Sod1), manganese superoxide dismutase (Sod2), catalase (Cat), heme oxygenase-1 (Hmox1), nuclear factor erythroid 2 related factor 2 (Nfe2l2), γ-glutamylcysteine synthetase (Gclm), and quinone oxidoreductase 1 (Nqo1) in mouse liver and spleen and downregulated expression of inducible nitric oxide synthase (Nos2). Western blot analysis revealed that LP-KSFY02 effectively upregulated protein expression of SOD1, SOD2, CAT, GSH1, and GSH2 in mouse liver and spleen tissues. Therefore, LP-KSFY02 can effectively prevent d-galactose-induced oxidative aging in mice. Its efficacy was superior to that of Lactobacillus delbrueckii ssp. bulgaricus (LDSB) and vitamin C, which are commonly used in the medical field as antioxidants. Thus, LP-KSFY02 is a high-quality strain with probiotic potential.

Antifungal and antimycotoxigenic effect of Lactobacillus plantarum CRL 778 at different water activity values.

Ochratoxin A (OTA) is a mycotoxin produced by filamentous fungi with high impact in food safety due to its toxicity. In the last decade, the presence of OTA was widely reported in different foods. In this study, the ability of Lactobacillus (L.) plantarum CRL 778 to control growth and OTA production by Aspergillus (A.) niger 13D strain, at different water activity (aw) values (0.955, 0.964, 0.971, 0.982, and 0.995) was determined in vitro. Both parameters were significantly (p<0.05) reduced by the lactobacilli and the effect depended on aw. Greatest growth rate inhibition (46.9%) was obtained at aw=0.995, which is the most suitable value for growth and production of antifungal metabolites (lactic acid, acetic acid, phenyllactic and hydroxyl-phenyllactic acids) by L. plantarum CRL 778. Besides, morphological changes and inhibition of melanin synthesis were observed in colonies of A. niger 13D in presence of L. plantarum CRL 778 at aw ranged between 0.971 and 0.995. In addition, maximum reduction (90%) of OTA production took place at aw=0.971, while inhibition of fungi growth was more evident at aw=0.995. These findings suggest that L. plantarum CRL 778 could be used for control of ochratoxigenic fungal growth and OTA contamination in different fermented foods with aw values between 0.971 and 0.995.

Antibacterial activity of Lactobacillus plantarum isolated from Tibetan yaks.

The main purpose of our study was to isolate the Lactobacillus strains from Tibetan yaks, which may have antibacterial activity. Three Lactobacillus plantarum (L. plantarum) strains named LP1, LP2, LP3 and one Pediococcus pentosaceus (P. pentosaceus) named PT2 were isolated from fecal samples of Tibetan yaks. We regarded indigenous Escherichia coli (E. coli ATCC 25922) and Staphylococcus aureus (S. aureus ATCC 25923) as indicator pathogens. The Bacteriocins derived from these isolated strains manifested high antibacterial activity against E. coli, the highest activity was observed in the case of LP1. On the other hand, PT2 had the most powerful bacteriostatic ability against S. aureus. In addition, all strains were positive for Ent A, which plays an important role in secreting pediocin-like bacteriocins and shows potential probiotic traits of bile and low PH tolerance. Overall, L. plantarum strains in present study could be employed as effective antibacterial substances and can help to remit the problem of antibiotic resistance in veterinary medicine.

Effect of a probiotic Lactobacillus plantarum TN8 strain on trinitrobenzene sulphonic acid-induced colitis in rats.

This study aimed to investigate the potential effects of an oral treatment by a newly isolated probiotic Lactobacillus plantarum TN8 strain on trinitrobenzene sulphonic acid (TNBS)-induced colitis in Wistar rats. Thus, 18 rats were divided into three groups (n = 6 per group): group 1 (control) - rats not receiving TNBS application; group 2 - rats receiving an intrarectal TNBS infusion (100 mg/kg TNBS dissolved in ethanol); and group 3 - rats treated with intragastrical TN8 strain once per day (for 5 days before TNBS induction). The performance and the effects of the probiotic treatment were evaluated using a series of histological, biophysical and biochemical analyses. The results have shown that the treatment with the L. plantarum TN8 strain improves the body weight and reduces the diarrhoea, colonic mucosal inflammation and colon shortening. TN8-treated rats showed a significant decrease in the total cholesterol content from 1.86 (for group 2) to 1.32 mmol/l and in triglyceride (TG) content from 2.09 (for group 2) to 1.23 mmol/l. Furthermore, the findings revealed that the high-density lipoprotein (HDL) cholesterol contents increased from 0.95 to 1.02 mmol/l. The histological studies have confirmed that the architecture of the liver and kidney tissues of the TN8-treated rats were found to be improved. Overall, the results suggest that the L. plantarum TN8 presents promising perspectives for the development of safe and cost-effective agents for the prevention or alleviation of several intestinal pathologies.

[Isolation, identification and fermentation optimization of lactic acid bacteria for aquaculture water purification].

Objective: In order to get excellent strains for aquiculture water purification, we screened lactic acid bacteria from the aquaculture environment and intestinal tract of shrimp. Methods: The potential water purification ability of lactic acid bacteria at normal and low temperature was evaluated in the simulated wastewater. Morphological physio-biochemical characteristics, 16S rRNA gene sequence analysis were used to identify strain r13. Single factor test and orthogonal-design experiment were applied to optimize fermentation for r13. Results: In total 136 lactic acid bacteria strains were isolated from 3 samples. The results of water purification test suggested r13 had higher removal ability of nitrite and ammonia from water. After 72 h treatment by r13, nitrite with 11.5 mg/L in the water was completely removed and ammonia degradation rate was 29.1% with 13.0 mg/L original concentration. According to morphological, physio-biochemical characteristics and 16S rRNA gene sequence analysis, r13 was identified as Lactobacillus plantarum. The optimal fermentation condition for r13 was 6.0 g/L yeast extract, 20.0 g/L glucose, 4.0 g/L sodium acetate, 2.0 g/L diammonium hydrogen citrate, 2.0 g/L monopotassium phosphate, 50 mL tomato juice, with inoculation rate 5% (V/V), at pH 6.0 and 34℃. Under this condition cultured for 72 h, the bacterial biomass reached 28.4 g/L wet weight and cell counting reached 4.4×109 CFU/mL. Conclusion: Considering high nitrite removal ability, we suggested that r13 would be promising microorganism for water purification in aquiculture.

Antibacterial metabolites secreted under glucose-limited environment of the mimicked proximal colon model by lactobacilli abundant in infant feces.

The most abundance of anti-Salmonella lactic acid bacteria (LAB) was found in feces of naturally born, exclusively breastfed Thai infants. Six strains of Lactobacillus plantarum and one strain of Lactobacillus paracasei were selected and identified. In the co-cultivation assay, L. plantarum subsp. plantarum I62 showed the strongest and broadest antibacterial activity against Escherichia coli, Shigella sonnei, Salmonella Paratyphi A, and Salmonella Typhimurium SA 2093 under the mimicked proximal colon condition, in which glucose and other nutrients were limited. According to GC-MS analysis, the major antibacterial contribution of organic acids secreted by L. plantarum I62 grown in the presence of glucose was dramatically reduced from 95.8 to 41.9 % under glucose-limited niche. The production of low-pK a acids, such as lactic, 1,2-benzenedicarboxylic, and 3-phenyllactic acids, was remarkably dropped. Surprisingly, higher-pK a acids such as 5-chlorobenzimidazole-2-carboxylic, pyroglutamic, palmitic, and oleic acids were enhanced. Moreover, cyclic dipeptides, ketones, alkanes, alcohols, and miscellaneous compounds, which were pH-independent antibacterial metabolites, became dominant. The electron microscopy strongly supported the synergistic attacks of the multiple antibacterial components targeting outer and cytoplasmic membranes leading to severe leakage and cell disruption of Salmonella Typhimurium. This strain poses to be a potential probiotic candidate for effectively controlling and treating human foodborne bacterial infection.

Biodiversity and technological potential of lactic acid bacteria isolated from spontaneously fermented amaranth sourdough.

UNLABELLED: Spontaneous fermented sourdoughs prepared from amaranth flour were investigated for the presence of autochthonous lactic acid bacteria (LAB) predominating microbiota. The doughs were fermented with daily backslopping on a laboratory scale at 30°C for 10 days. LAB counts ranged from 2·60 to 8·54 log CFU g(-1) with a pH declined from 6·2 to 3·8 throughout fermentation. The combined use of randomly amplified polymorphic DNA (RAPD)-PCR analysis and sequence analysis of 16S rRNA was applied for LAB intraspecies differentiation and taxonomic identification, respectively. Enterococcus, Pediococcus and Lactobacillus species were present in amaranth sourdoughs (AS). After the first refreshment step, Lactobacillus plantarum dominated AS until the end of fermentation. In coincidence, when DGGE analysis was performed, the occurrence of a progressive change in bacterial communities allowed the selection of Lact. plantarum as a dominant species. Moreover, technological, functional and safety characteristics of representative RAPD-biotypes were investigated. Lact. plantarum CRL1898 was selected as a potential candidate for gluten-free amaranth sourdough starter. SIGNIFICANCE AND IMPACT OF THE STUDY: Nowadays, there is an increasing interest in ancient noncereal gluten-free (GF) crops such as amaranth, due to their reported nutritional and health benefits. However, the use of these grains is still limited to traditional foods and bread making processes that are not yet well standardized. Results on the dynamics of autochthonous lactic acid bacteria (LAB) microbiota during laboratory spontaneous amaranth sourdoughs (AS) fermentation will contribute to overcome challenges for GF-fermented products development. In addition, knowledge about LAB diversity involving Enterococcus, Pediococcus and Lactobacillus species, with Lactobacillus plantarum predominating during AS fermentation, and their technological and functional properties provides the basis for the selection of autochthonous strains as starters cultures for novel gluten-free bakery products with enhanced nutritional, sensory and/or safety quality.

Physiological and transcriptional responses and cross protection of Lactobacillus plantarum ZDY2013 under acid stress.

Acid tolerance responses (ATR) in Lactobacillus plantarum ZDY2013 were investigated at physiological and molecular levels. A comparison of composition of cell membrane fatty acids (CMFA) between acid-challenged and unchallenged cells showed that acid adaptation evoked a significantly higher percentage of saturated fatty acids and cyclopropane fatty acids in acid-challenged than in unchallenged cells. In addition, reverse transcription-quantitative PCR analysis in acid-adapted cells at different pH values (ranging from 3.0 to 4.0) indicated that several genes were differently regulated, including those related to proton pumps, amino acid metabolism, sugar metabolism, and class I and class III stress response pathways. Expression of genes involved in fatty acid synthesis and production of alkali was significantly upregulated. Upon exposure to pH 4.5 for 2 h, a higher survival rate (higher viable cell count) of Lactobacillus plantarum ZDY2013 was achieved following an additional challenge to 40 mM hydrogen peroxide for 60 min, but no difference in survival rate of cells was found with further challenge to heat, ethanol, or salt. Therefore, we concluded that the physiological and metabolic changes of acid-treated cells of Lactobacillus plantarum ZDY2013 help the cells resist damage caused by acid, and further initiated global response signals to bring the whole cell into a state of defense to other stress factors, especially hydrogen peroxide.

Complete genome sequences and comparative genome analysis of Lactobacillus plantarum strain 5-2 isolated from fermented soybean.

Lactobacillus plantarum is an important probiotic and is mostly isolated from fermented foods. We sequenced the genome of L. plantarum strain 5-2, which was derived from fermented soybean isolated from Yunnan province, China. The strain was determined to contain 3114 genes. Fourteen complete insertion sequence (IS) elements were found in 5-2 chromosome. There were 24 DNA replication proteins and 76 DNA repair proteins in the 5-2 genome. Consistent with the classification of L. plantarum as a facultative heterofermentative lactobacillus, the 5-2 genome encodes key enzymes required for the EMP (Embden-Meyerhof-Parnas) and phosphoketolase (PK) pathways. Several components of the secretion machinery are found in the 5-2 genome, which was compared with L. plantarum ST-III, JDM1 and WCFS1. Most of the specific proteins in the four genomes appeared to be related to their prophage elements.