Complete genome sequence of Lactobacillus plantarum LZ206, a potential probiotic strain with antimicrobial activity against food-borne pathogenic microorganisms

Functional Characterization of Lactobacillus plantarum Isolated from Cow Milk and the Development of Fermented Coconut and Carrot Juice Mixed Beverage

Screening probiotics are crucial for assessing their safety, security, and further production of functional foods for human health. The present study aimed to isolate and identify bacteria from raw cow's milk samples that exhibit health benefits upon consumption. We characterized the probiotic properties of Lactobacillus plantarum (also called Lactiplantibacillus plantarum) strains CMGC2 and CMJC7 isolated from cow milk by in vitro study. The strains exhibited tolerance to simulated gastric conditions and were further identified by 16S rRNA sequencing as Lactobacillus plantarum (L. plantarum) CMGC2 and CMJC7. Both isolates were evaluated in vitro for their probiotic attributes, viz. hydrophobicity, autoaggregation, co-aggregation, lysozyme tolerance, antibacterial activity, antibiotic susceptibility, hemolytic activity, and phenol tolerance. The isolates CMGC2 and CMJC7 showed excellent probiotic attributes; hence, both strains were selected to produce coconut and carrot juice mixed beverages (CCMB). The CCMB was evaluated for the pH, acid-production rate, and total viable bacterial counts. The results showed that the CCMB was an excellent medium for the growth of CMGC2 and CMJC7 as it supported adequate growth of organisms (8.93 CFU/mL and 8.68 CFU/mL, respectively) even after 48 h of incubation. In conclusion, CMGC2 and CMJC7 can be used to develop different beverages possessing nutritive and probiotic values, and these beverages can be used for producing unique products.

Complete Genome Sequence of a Novel Lactobacillus paracasei TK1501 and Its Application in the Biosynthesis of Isoflavone Aglycones

Lactobacillus strains are considered safe and healthy probiotics for manufacturing “natural food” products; this is due to their ability to produce bioactive compounds that reduce the incidence of various human diseases. Lactobacillus paracasei TK1501 is a novel probiotic strain isolated from naturally fermented congee; and can produce a high yield of genistein, one of the most widely studied isoflavone aglycones with plenty of physiological functions. To better understand the molecular basis of isoflavone aglycones biosynthesis, the complete 2,942,538 bp genome of L. paracasei TK1501 was sequenced and assembled; a group of genes that are involved in isoflavone aglycones production were identified. Of note, a β-glucosidase was analyzed in the L. paracasei TK1501. Moreover, we also found that L. paracasei TK1501 could be used in soymilk fermentation; which would remarkably increase the contents of genistein, daidzein, and glycitein. This work was meaningful to the application of L. paracasei TK1501 and the molecular mechanism analysis of isoflavone aglycones biosynthesis in Lactobacillus strains.

Comparative Genomics of Lactiplantibacillus plantarum: Insights Into Probiotic Markers in Strains Isolated From the Human Gastrointestinal Tract and Fermented Foods

Lactiplantibacillus (Lpb.) plantarum is a versatile species commonly found in a wide variety of ecological niches including dairy products and vegetables, while it may also occur as a natural inhabitant of the human gastrointestinal tract. Although Lpb. plantarum strains have been suggested to exert beneficial properties on their host, the precise mechanisms underlying these microbe-host interactions are still obscure. In this context, the genome-scale in silico analysis of putative probiotic bacteria represents a bottom-up approach to identify probiotic biomarkers, predict desirable functional properties, and identify potentially detrimental antibiotic resistance genes. In this study, we characterized the bacterial genomes of three Lpb. plantarum strains isolated from three distinct environments [strain IMC513 (from the human GIT), C904 (from table olives), and LT52 (from raw-milk cheese)]. A whole-genome sequencing was performed combining Illumina short reads with Oxford Nanopore long reads. The phylogenomic analyses suggested the highest relatedness between IMC513 and C904 strains which were both clade 4 strains, with LT52 positioned within clade 5 within the Lpb. plantarum species. The comparative genome analysis performed across several Lpb. plantarum representatives highlighted the genes involved in the key metabolic pathways as well as those encoding potential probiotic features in these new isolates. In particular, our strains varied significantly in genes encoding exopolysaccharide biosynthesis and in contrast to strains IMC513 and C904, the LT52 strain does not encode a Mannose-binding adhesion protein. The LT52 strain is also deficient in genes encoding complete pentose phosphate and the Embden-Meyerhof pathways. Finally, analyses using the CARD and ResFinder databases revealed that none of the strains encode known antibiotic resistance loci. Ultimately, the results provide better insights into the probiotic potential and safety of these three strains and indicate avenues for further mechanistic studies using these isolates.

Assessments of Probiotic Potentials of Lactiplantibacillus plantarum Strains Isolated From Chinese Traditional Fermented Food: Phenotypic and Genomic Analysis

The lack of rapid and effective approaches to determine the health benefits of strains is one of the main challenges affecting the selection of probiotics from large numbers of candidates. In this study, the probiotic potential of 44 Lactiplantibacillus plantarum strains isolated from different Chinese traditional fermented foods was evaluated, including acid and bile salt resistance, adhesion ability, survival in simulated human gastrointestinal transit, antioxidant activity, bile salt hydrolase (BSH) activity, and antibacterial activity. All tested L. plantarum strains showed high antioxidant capacity, BSH activity, and antibacterial activity. Among the strains, B652, C232, D444, and E932 were identified as the best comprehensive performed strains, which were selected for whole-genome sequencing, in order to provide clear information and identify key genes responsible for functional characteristics in vitro. It demonstrated that the antioxidant activity, adhesion activity, and ability to survive in the simulated gastric environment were found to be closely correlated with antioxidant enzyme encoding genes, cell-surface protein-encoding genes, and stress response genes, respectively. The numbers of functional genes present in strains might decide their performance in probiotic profile evaluation. The outcome of the study could support the development of a novel approach for the screening and identification of probiotics.

Spatial and Temporal Persistence of Fluorescent Lactiplantibacillus plantarum RS-09 in Intestinal Tract

The beneficial effects of the probiotic strain Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) are based on its adherence and colonization ability in the gut. However, little is known about the migration and long-term gut colonization of the strain. This study evaluated the gut colonization modes of Lactiplantibacillus plantarum RS-09 to identify the strain with long-term gut colonization potential. We established CFDA/SE-labeled RS-09 to study the temporal and spatial distribution of RS-09 in the intestine as well as to analyze its persistence in different parts of the intestine by flow cytometry. This study has shown that the RS-09 strain maintains strong adhesion abilities under acid (pH 2.5) and base (pH 8.5) conditions. In addition, CFDA/SE can be used as an indicator for the labeling of L. plantarum RS-09 in the intestinal tract in vivo. We established a growth kinetics model of RS-09 to elucidate its persistence in the intestine. In vivo persistence experiments showed that the persistence rate of RS-09 was the highest in the cecum (69.5%) and the lowest in the duodenum (12.8%) at 96 h. After 20 days, RS-09 was predominantly localized in the cecum and colon steadily. These studies provide new insights into the long-term persistence of L. plantarum in the gastrointestinal tract. The CFDA/SE label system may be used to study the in vivo colonization dynamics of other probiotic strains.

Whole genome and acid stress comparative transcriptome analysis of Lactiplantibacillus plantarum ZDY2013

Previous study has reported that Lactiplantibacillus plantarum ZDY2013 which was screened from traditional Chinese fermented soybeans has a strong acid resistance. The purpose of this study was to uncover the genes potentially related to its genetic adaptation and probiotic profiles, based on comparative genomic and comparative transcriptome analysis. We got the basic information about L. plantarum ZDY2013 and identified genes which are related to genetic adaptation and probiotic profiles, including carbohydrate transport and metabolism, cell wall/membrane/envelope biogenesis, proteolytic enzyme systems and amino acid biosynthesis, CRISPR adaptive immunity, stress responses, ability to adhere to the host intestinal wall, exopolysaccharide (EPS) biosynthesis, and bacteriocin biosynthesis. Comparative transcriptome showed CK group (normal MRS culture L. plantarum ZDY2013) and SCL group (pH 3.0 MRS culture L. plantarum ZDY2013) had 652 significant differentially expressed genes including 310 up-regulated genes and 342 down-regulated genes. Besides that, these genes had been classified through KEGG and GO functional annotation. In addition, we also found top 20 KEGG pathways adjusted to acid stress. Then, some genes were selected to verify the transcriptome analysis and explore the mechanism of how L. plantarum ZDY2013 tolerate acid stress. We found that some genes of ABC transporter, phosphotransferase system, oxidation reduction process, membrane transporter and phosphorylation metabolism process had a significant change. These results suggested that comparative characterization of the L. plantarum ZDY2013 genome and transcriptome provided the genetic basis for further elucidating the functional mechanisms of it.

Cytotoxicity, apoptosis, and IL-8 gene expression induced by some foodborne pathogens in presence of Bacillus coagulans in HT-29 cells

Food poisoning caused by bacteria is one of the most important concerns in food hygiene. The use of probiotics in prevention, control, and treatment of these infections has been considerably increased in recent years. This study evaluated the effect of B. coagulans cell free supernatant (CFS) on growth of Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, non-pathogenic Escherichia coli, and Escherichia coli 0157:H7 by the broth dilution method. The cytotoxicity, and apoptosis induced by pathogens alone and in co-culture with B. coagulans or its CFS were measured by trypan blue, and fluorescence staining methods. The expression level of interleukin-8 (IL-8) cytokine-encoding genes was also investigated by a qRT-PCR assay in all pathogens and co-cultured groups in HT-29 cells. Our results showed that 4% B. coagulans CFS reduced pathogen growth. The highest rate of growth inhibition was observed in L. monocytogenes. We also found that B. coagulans, and its 4% CFS reduced the cytotoxic effects of pathogens, with the exception of S. aureus. Non-pathogenic E. coli also had no significant cytotoxic effect on the cells. Examination of the treated cells with acridine orange/ethidium bromide staining showed reductions in the rate of cell damage (including early apoptosis, late apoptosis, and necrosis) in pathogen-probiotic co-cultures. Furthermore, we showed that co-culture of pathogens with B. coagulans significantly down-regulated IL-8 gene expression (P < 0.05). The greatest down-regulation compared with pathogen alone was observed in S. aureus. Hence, B. coagulans can be considered as an appropriate probiotic to diminish cytotoxicity, and inflammatory response of enteropathogenic bacteria.

Update of Probiotics in Human World: A Nonstop Source of Benefactions till the End of Time

Lactic acid bacteria (LAB) are known for their biotechnological potential. Moreover, LAB are distinguished by amazing criteria: Adjusting the intestinal environment, inhibiting pathogenic microbes in the gastrointestinal tract, ability to reduce pathogen adhesion activity, improving the balance of the microbiota inside the intestine, capabilities of regulating intestinal mucosal immunity, and maintaining intestinal barrier function. The escalating number of research and studies about beneficial microorganisms and their impact on promoting health has attracted a big interest in the last decades. Since antiquity, various based fermented products of different kinds have been utilized as potential probiotic products. Nevertheless, the current upsurge in consumers' interest in bioalternatives has opened new horizons for the probiotic field in terms of research and development. The present review aims at shedding light on the world of probiotics, a continuous story of astonishing success in various fields, in particular, the biomedical sector and pharmaceutical industry, as well as to display the importance of probiotics and their therapeutic potential in purpose to compete for sturdy pathogens and to struggle against diseases and acute infections. Shadows and future trends of probiotics use are also discussed.

Inhibition of Streptococcus mutans Biofilm Formation and Virulence by Lactobacillus plantarum K41 Isolated From Traditional Sichuan Pickles

Among cariogenic microbes, Streptococcus mutans is considered a major etiological pathogen of dental caries. Lactobacilli strains have been promoted as possible probiotic agents against S. mutans, although the inhibitory effect of Lactobacilli on caries has not yet been properly addressed. The objective of this study was to screen Lactobacillus strains found in traditional Sichuan pickles and to evaluate their antagonistic properties against S. mutans in vitro and in vivo. In the current study, we analyzed 54 Lactobacillus strains isolated from pickles and found that strain L. plantarum K41 showed the highest inhibitory effect on S. mutans growth as well as on the formation of exopolysaccharides (EPS) and biofilm in vitro. Scanning electron microscopy (SEM) and confocal laser scanning microscope (CLSM) revealed the reduction of both EPS and of the network-like structure in S. mutans biofilm when these bacteria were co-cultured with strain L. plantarum K41. Furthermore, when rats were treated with strain L. plantarum K41, there was a significant reduction in the incidence and severity of dental caries. Due to K41's origin in a high salinity environment, it showed a high tolerance to acids and salts. This may give this strain an advantage in harsh oral conditions. Results showed that L. plantarum K41 isolated from traditional Sichuan pickles effectively inhibited S. mutans biofilm formation and thus possesses a potential inhibitory effect on dental caries in vivo.

Next-generation sequencing to elucidate adaptive stress response and plantaricin genes among Lactobacillus plantarum strains

Aim: The objective of this study was to identify the genes involved in plantaricin synthesis and adaptive stress response in four Lactobacillus plantarum strains (AS-6, AS-8, AS-9 and AS-10) and one Lactobacillus paraplantarum strain (AS-7) for their usage in medicine and industry. Materials & methods: Whole genomes of these strains were sequenced by a high-throughput sequencing technique known as next-generation sequencing via Ilumina MiSeq platform and the genes were identified by using various bioinformatics tools and software. Results: Plantaricin genes (plnD, plnE, plnF, plnG, plnI) and genes regulating response to temperature, pH, bile salt, osmotic and oxidative stress were identified in all strains. Conclusion: Lactobacilli could be an option to combat antimicrobial resistance and might replace harmful antibiotics in future.

Survivability of alginate-microencapsulated Lactobacillus plantarum during storage, simulated food processing and gastrointestinal conditions

A comparison between the most investigated alginate-based encapsulating agents was performed in the current study. Here, the survivability of Lactobacillus plantarum microencapsulated with alginate (Alg) combined with skim milk (Sm), dextrin (Dex), denatured whey protein (DWP) or coated with chitosan (Ch) was evaluated after exposure to different heat treatments and in presence of some food additives, during storage and under simulated gastrointestinal condition. In addition, the encapsulated cells were evaluated for production of different bioactive compounds such as exopolysacchar. ides and antimicrobial substances compared with the unencapsulated cells. The results showed that only Alg-Sm maintained the viability of the cells >106 cfu/g at the pasteurization temperature (65 °C for 30 min). Interestingly, storage under refrigeration conditions increased the viability of L. plantarum entrapped within all the tested encapsulating agents for 4 weeks. However, under freezing condition, only Alg-DWP and Alg-Sm enhanced the survival of the entrapped cells for 3 months. All the microencapsulated cells were capable of growing at the different NaCl concentrations (1%-5%) except for cells encapsulated with Alg-Dex, showed viability loss at 3% and 5% NaCl concentrations. Tolerance of the microencapsulated cells toward organic acids was varied depending on the type of organic acid. Alg-Ch and Alg-Sm provide better survival for the cells under simulated gastric juice; however, all offer a good survival for the cells under simulated intestinal condition. Our findings indicated that Alg-Sm proved to be the most promising encapsulating combination that maintains the survivability of L. plantarum to the recommended dose level under almost all the stress conditions adopted in the current study. Interestingly, the results also revealed that microencapsulation does not affect the metabolic activity of the entrapped cells and there was no significant difference in production of bioactive compounds between the encapsulated and the unencapsulated cells.

Design and preparation of antimicrobial meat wrapping nanopaper with bacterial cellulose and postbiotics of lactic acid bacteria

Lyophilized postbiotics of Lactobacillus plantarum was prepared and impregnated in bacterial nanocellulose (BNC) by ex-situ method to develop an antimicrobial ground meat wrapping nanopaper. The postbiotics incorporated BNC (P-BNC) films were optimized by response surface methodology and their antimicrobial activity against Listeria monocytogenes were examined. The BNC with postbiotics at 21.21% concentration and 28 min impregnation time was chosen as an optimized P-BNC film. The FTIR results confirmed the immobilization of postbiotics in BNC. The P-BNC film represented a significant reduction (~5 log cycles) in L.monocytogenes counts in ground meat at the end of the storage period (9 days at 4 °C). Meat wrapped by P-BNC film displayed a significant decrease in total mesophilic and psychrophiles count and TBA values than the controls. BNC can be considered as a proper carrier for development of antimicrobial film using postbiotics of LAB for food application.

Cell-free supernatants from cultures of lactic acid bacteria isolated from fermented grape as biocontrol against Salmonella Typhi and Salmonella Typhimurium virulence via autoinducer-2 and biofilm interference

Background

Salmonella Typhi and Salmonella Typhimurium are the causative pathogens of salmonellosis, and they are mostly found in animal source foods (ASF). The inappropriate use of antibiotics enhances the possibility for the emergence of antibiotic resistance in pathogens and antibiotic residue in ASF. One promising alternative to antibiotics in animal farming is the use of lactic acid bacteria (LAB).

Methods

The present study was carried out the cells and/or the cell-free culture supernatants (CFCS) from beneficial LAB against S. Typhi and S. Typhimurium. The antibacterial mechanisms of LAB-CFCS as biocontrol agents against both Salmonella serovars were investigated through the analysis of anti-salmonella growth activity, biofilm inhibition and quorum quenching activity.

Results

Among 146 LAB strains isolated from 110 fermented food samples, the 2 strong inhibitory effect strains (WM33 and WM36) from fermented grapes against both Salmonella serovars were selected. Out of the selected strains, WM36 was the most effective inhibitor, which indicated S. Typhi by showing 95.68% biofilm inhibition at 20% biofilm inhibition concentration (BIC) and reduced 99.84% of AI-2 signaling interference. The WM33 was the best to control S. Typhimurium by producing 66.46% biofilm inhibition at only 15% BIC and 99.99% AI-2 signaling a reduction. The 16S rDNA was amplified by a polymerase chain reaction (PCR). The selected isolates were identified as Weissella viridescens WM33 and Weissella confusa WM36 based on nucleotide homology and phylogenetic analysis.

Conclusion

The metabolic extracts from Weissella spp. inhibit Salmonella serovars with the potential to be used as biocontrol agents to improve microbiological safety in the production of ASF.

Genetic Variation of pln Loci Among Probiotic Lactobacillus plantarum Group Strains with Antioxidant and Cholesterol-Lowering Ability

In the present study, 14 different plantaricin-encoding genes of pln loci were studied and compared to available sequences from public domain database of probiotic Lactobacillus plantarum strains. Based upon the presence and absence of selected genes, pln locus was grouped into eight clusters. Further, quantitative real-time PCR (qRT-PCR) analysis for seven genes has discriminated the complex pln locus into five types which includes WCFS1 (in Lactobacillus plantarum subsp. plantarum MCC 2976 and MCC 2974 and Lactobacillus paraplantarum MCC 2978), closely related to J51 (in Lb. paraplantarum MCC 2973 and MCC 2977), J23 (in Lb. plantarum MTCC 5422), NC8 (in Lb. paraplantarum MTCC 9483), and a new E1 type (in Lb. plantarum subsp. plantarum E1). It was observed that the plnA, EF, NC8βα, NC81F, NC8HK, and G were expressed in E1 strain. Further, southern hybridization confirmed the chromosome-encoded plantaricin in Lb. plantarum group (LPG) strains. Several PCR assays and DNA sequence analysis of the regions amplified in pln loci of E1 isolate suggested a hybrid variant of NC8 and J51 plantaritypes. This indicates the wide distribution of plantaricin with remarkable variation, diversity, and plasticity among the LPG strains of vegetable origin. Further, the selected strains were able to reduce the growth of Kocuria rhizophila ATCC 9341 by 40-54% within 6 h of co-incubation under in vitro pathogen exclusion assay. These isolates also possessed cholesterol-lowering and antioxidant activity suggesting their application in the development of functional foods.

Whole Genome Analysis of Lactobacillus plantarum Strains Isolated From Kimchi and Determination of Probiotic Properties to Treat Mucosal Infections by Candida albicans and Gardnerella vaginalis

Three Lactobacillus plantarum strains ATG-K2, ATG-K6, and ATG-K8 were isolated from Kimchi, a Korean traditional fermented food, and their probiotic potentials were examined. All three strains were free of antibiotic resistance, hemolysis, and biogenic amine production and therefore assumed to be safe, as supported by whole genome analyses. These strains demonstrated several basic probiotic functions including a wide range of antibacterial activity, bile salt hydrolase activity, hydrogen peroxide production, and heat resistance at 70°C for 60 s. Further studies of antimicrobial activities against Candida albicans and Gardnerella vaginalis revealed growth inhibitory effects from culture supernatants, coaggregation effects, and killing effects of the three probiotic strains, with better efficacy toward C. albicans. In vitro treatment of bacterial lysates of the probiotic strains to the RAW264.7 murine macrophage cell line resulted in innate immunity enhancement via IL-6 and TNF-α production without lipopolysaccharide (LPS) treatment and anti-inflammatory effects via significantly increased production of IL-10 when co-treated with LPS. However, the degree of probiotic effect was different for each strain as the highest TNF-α and the lowest IL-10 production by the RAW264.7 cell were observed in the K8 lysate treated group compared to the K2 and K6 lysate treated groups, which may be related to genomic differences such as chromosome size (K2: 3,034,884 bp, K6: 3,205,672 bp, K8: 3,221,272 bp), plasmid numbers (K2: 3, K6 and K8: 1), or total gene numbers (K2: 3,114, K6: 3,178, K8: 3,186). Although more correlative inspections to connect genomic information and biological functions are needed, genomic analyses of the three strains revealed distinct genomic compositions of each strain. Also, this finding suggests genome level analysis may be required to accurately identify microorganisms. Nevertheless, L. plantarum ATG-K2, ATG-K6, and ATG-K8 demonstrated their potential as probiotics for mucosal health improvement in both microbial and immunological contexts.

Probiotic potential of novel Lactobacillus strains isolated from salted-fermented shrimp as antagonists for Vibrio parahaemolyticus

Lactobacillus strains have been considered good candidates as biological control agents for prevention or treatment of plant and animal infections. One L. plantarum strain FB003 and three strains (FB011, FB081, and FB110) which closed to L. sakei were isolated from fermented and salted shrimp and their abilities in inhibiting growth of Vibrio parahaemolyticus were characterized. These strains were selected as potential probiotics based on their oro-gastro-intestinal resistance, gut colonization, adhesion to Caco-2 cells, antimicrobial activities, antibiotic resistance, and safety aspects. Results of this study revealed that these isolates possessed high aggregation activities against pathogens in host intestines. Strain FB011 strain showed higher coaggregation and immunomodulatory activity in the gastro-intestinal tract than L. plantarum. These difference effects of Lactobacillus strains provide valuable information about using them to prevent Vibrio infections in the aquaculture industry.

The complete genome sequence of Lactobacillus plantarum LPL-1, a novel antibacterial probiotic producing class IIa bacteriocin

Bacteriocins are antibacterial proteins or peptides synthesized by ribosomes to inhibit or kill both closely related and non-related bacterium. Class IIa bacteriocins possess high activity against foodborne pathogen Listeria monocytogenes. A novel strain Lactobacillus plantarum LPL-1 was isolated from fermented fish and considered as a bacteriocin producing probiotic with great antibacterial activity against Listeria monocytogenes 54002. The complete genome of L. plantarum LPL-1 contains one circular chromosome and plasmid. According to the genome, biosynthetic genes of bacteriocin including precursor, immunity protein,accessory protein and transporter protein were identified; and biosynthetic mechanism of class IIa bacteriocin was also further analyzed. The antibacterial activity of purified bacteriocin against L.monocytogenes54002 was determined and the diameter of inhibition zone was about 16.6 mm by vernier caliper. This work provided the complete genome information of L. plantarum LPL-1 that could benefit for understanding the biosynthetic mechanism of class IIa bacteriocin as well as the potential application of L. plantarum LPL-1 in nutraceutical and pharmaceutical.

Complete Genome Sequence of Streptococcus thermophilus KLDS 3.1003, A Strain with High Antimicrobial Potential against Foodborne and Vaginal Pathogens

Lactic acid bacteria play increasingly important roles in the food industry. Streptococcus thermophilus KLDS 3.1003 strain was isolated from traditional yogurt in Inner Mongolia, China. It has shown high antimicrobial activity against selected foodborne and vaginal pathogens. In this study, we investigated and analyzed its complete genome sequence. The S. thermophilus KLDS 3.1003 genome comprise of a 1,899,956 bp chromosome with a G+C content of 38.92%, 1,995 genes, and 6 rRNAs. With the exception of S. thermophilus M17TZA496, S. thermophilus KLDS 3.1003 has more tRNAs (amino acid coding genes) compared to some S. thermophilus strains available on the National Centre for Biotechnology Information database. MG-RAST annotation showed that this strain has 317 subsystems with most genes associated with amino acid and carbohydrate metabolism. This strain also has a unique EPS gene cluster containing 23 genes, and may be a mixed dairy starter culture. This information provides more insight into the molecular basis of its potentials for further applications in the dairy and allied industries.

Complete genome sequence of bacteriocin-producing Lactobacillus plantarum KLDS1.0391, a probiotic strain with gastrointestinal tract resistance and adhesion to the intestinal epithelial cells

Lactobacillus plantarum KLDS1.0391 is a probiotic strain isolated from the traditional fermented dairy products and identified to produce bacteriocin against Gram-positive and Gram-negative bacteria. Previous studies showed that the strain has a high resistance to gastrointestinal stress and has a high adhesion ability to the intestinal epithelial cells (Caco-2). We reported the entire genome sequence of this strain, which contains a circular 2,886,607-bp chromosome and three circular plasmids. Genes, which are related to the biosynthesis of bacteriocins, the stress resistance to gastrointestinal tract environment and adhesive performance, were identified. Whole genome sequence of Lactobacillus plantarum KLDS1.0391 will be helpful for its applications in food industry.

Comparison of Antibacterial Activity of Lactobacillus plantarum Strains Isolated from Two Different Kinds of Regional Cheeses from Poland: Oscypek and Korycinski Cheese

Oscypek and korycinski are traditional Polish cheeses, exclusively produced in Tatra and in Podlasie region, respectively, produced from raw, unpasteurized milk. The 29 Lactobacillus plantarum strains were isolated on MRS agar from 12 cheese samples and used as a material for study. The main purpose of the work was to assess the antimicrobial properties and recognition of selected strains for the unique antagonistic activity and preservation role in food. It has been found that the highest antimicrobial activity was observed in the case of L. monocytogenes strains; however, the level of that activity was different depending on the Lb. plantarum strain. Strains from oscypek produced broad spectrum, and a few strains isolated from korycinski cheese produced a narrow spectrum of antimicrobial compounds, other than organic acids and hydrogen peroxide. Moreover, the antagonistic activity shown by Lb. plantarum strains is connected with the source from which a given strain was isolated. Strains isolated from oscypek cheese represented stronger activity against L. monocytogenes, whereas strains isolated from korycinski cheese were more active against E. coli. Strains Lb. plantarum Os13 and Kor14 could be considered as good candidates for protective cultures to extend durability of food products.

Some current applications, limitations and future perspectives of lactic acid bacteria as probiotics

Several mechanism and non-mechanism-based studies supporting the claim that lactic acid bacteria (LAB) strains confer health benefits and play immune-modulatory roles were examined in this review. Probiotic applications of LAB on global burdens such as obesity and type-2 diabetes were discussed as well as the use of yoghurt and ice cream as important vehicles to convey several beneficial LAB strains. Probiotic and symbiotic dairy products may be used in the nearest future to treat a variety of health disorders. Current studies suggest that lactic acid bacteria possess anti-obesity and anti-diabetic propensities on their hosts and thus can play a crucial role in human health care. Research in the rheological and physicochemical properties of ice cream as well as its applications are also on the increase. These applications face certain hurdles including technological (for less developed countries), consumer acceptability of new functional foods may be influenced by culture, ethics or religion. There is need for more studies on the genetic basis for probiotic properties which will give further understanding regarding novel manipulation skills and applicability in nutrition and health sectors. More studies confirming the direct effects of probiotic LABs in lowering the spread of food-borne and other pathogens are also anticipated.

Antibacterial effects of Lactobacillus isolates of curd and human milk origin against food-borne and human pathogens

This study was undertaken to assess the antibacterial efficacy of lactobacilli isolated from curd and human milk samples. Identities of thirty-one different lactobacilli (20 from curd and 11 from human milk) were confirmed by genus-specific PCR and 16S rRNA-based sequencing. These strains belonged to five species, Lactobacillus casei, L. delbrueckii, L. fermentum, L. plantarum, and L. pentosus. Antibacterial activities of cell-free supernatants (CFSs) of all the Lactobacillus isolates were estimated through standard agar-well diffusion assay, against commonly occurring food-borne and clinically important human pathogens. None of the lactobacilli cell-free supernatant (CFS) exhibited inhibitory activity against four pathogens, namely Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Klebsiella pneumoniae. Bacillus cereus, Salmonella enterica serovar Typhi, and Shigella flexneri were moderately inhibited by majority of CFSs, whereas, weak activity was observed against Pseudomonas aeruginosa and Proteus mirabilis. CFS of some of the curd isolates displayed antagonistic activity against Streptococcus mutans; however, human milk lactobacilli did not displayed any inhibitory activity against them. As expected, Nisin (Nisaplin^®) showed inhibitory activity against Gram-positive, S. aureus, B. cereus, and L. monocytogenes. Interestingly, few of the examined CFSs exhibited inhibitory activities against both Gram-positive and Gram-negative pathogens. Findings from this study support the possibility to explore the tested lactobacilli and their CFSs as natural bio-preservatives, alone or in combination with approved bacteriocins in food and pharma formulations after validating their safety.