In vitro evaluation of probiotic potential of five lactic acid bacteria and their antimicrobial activity against some enteric and food-borne pathogens

Antibacterial activity of lactobacilli from buffalo milk and yoghurt in Bandar-e Gaz, North-West Iran

A cross-sectional study was conducted from April to June 2016 to determine the inhibitory effect of Lactobacillus strains isolated from buffalo milk and yogurt in Bandar-e Gaz, Golestan province, North-West Iran. The raw milk and yogurt samples were collected and cultivated on MRS medium by anaerobical incubation at 37 °C for 48 h. The suspected colonies were identified on the basis of Gram’s staining and conventional biochemical tests. The antibacterial activity of the cell-free supernatant extracted from Lactobacillus strains was determined using the agar well diffusion method against standard strains Escherichia coli ATCC 11303, Staphylococcus aureus ATCC 29213, Bacillus cereus ATCC 19115, Listeria monocytogenes ATCC 19111, E. coli and S. aureus isolates from local cheese samples. A total of 10 Lactobacillus spp. were isolated and identified as L. plantarum, L. casei, L. acidophilus. L. plantarum A1 and L. acidophilus R1 exhibited relatively strong inhibitory effect against S. aureus and B. cereus, respectively. Both isolates had no inhibitory effect against L. monocytogenes. L. casei B1 showed moderate inhibitory effects against L. monocytogenes. This study showed that Lactobacilli from buffalo dairy products had good inhibitory activity towards Gram-positive indicator organisms and were one of the best choices to control these pathogens in food products.

Bacteriocin producing microbes with bactericidal activity against multidrug resistant pathogens

BACKGROUND

Bacteriocins are proteins or peptides synthesized by bacteria that show inhibitory or killing activities against various bacteria. Bacteriocins are mainly considered for effective alternatives to different commercial antibiotics, preservatives in the food and pharmaceutical industries.

OBJECTIVES

To screen and analyze novel bacteriocin-producing bacteria from the fermented food shidal for antibacterial activity against food pathogens and their molecular interactions studied through computationally.

METHODS

In this study, a strain Lactobacillus plantarum LA21 was isolated from the fermented food shidal identified based on morphological, biochemical, and 16S rDNA gene sequencing. The potent bacterium was subjected to improve bacteriocins production and characterized. Antimicrobial activity against drug-resistant bacteria and minimum inhibitory concentration (MIC) were determined. The bacteriocin was treated with proteolytic enzymes, and the mechanism of action on food pathogens was analyzed. Molecular docking studies were carried out as GLIDE module in the maestro tool of Schrodinger Software.

RESULTS

Bacteriocin was effective against pathogens such as Bacillus pumilus, Bacillus amyloliquefaciens, Staphylococcus aureus, and Listeria monocytogenes, with the most negligible MIC value was detected in L. monocytogenes. Furthermore, the depleted viability of bacterial cells indicated bacteriocin-induced cell lysis in L. monocytogenes via bactericidal activity. In addition, proteolytic enzyme digested bacteriocins revealed bacteriocin-like substances. Finally, molecular docking was performed to study the interactions between the targets and bacteriocins, results in relative intense contact with minimally 3 Å distance.

CONCLUSIONS

The characteristic features of these bacteriocin-like molecules revealed that L. plantarum LA21 is a novel bacteriocin-producing bacterial strain to prepare novel antimicrobial drugs, feed additives or preservatives for future use in livestock and food industries.

Pediococcus pentosaceus, a future additive or probiotic candidate

Background

Pediococcus pentosaceus, a promising strain of lactic acid bacteria (LAB), is gradually attracting attention, leading to a rapid increase in experimental research. Due to increased demand for practical applications of microbes, the functional and harmless P. pentosaceus might be a worthwhile LAB strain for both the food industry and biological applications.

Results

As an additive, P. pentosaceus improves the taste and nutrition of food, as well as the storage of animal products. Moreover, the antimicrobial abilities of Pediococcus strains are being highlighted. Evidence suggests that bacteriocins or bacteriocin-like substances (BLISs) produced by P. pentosaceus play effective antibacterial roles in the microbial ecosystem. In addition, various strains of P. pentosaceus have been highlighted for probiotic use due to their anti-inflammation, anticancer, antioxidant, detoxification, and lipid-lowering abilities.

Conclusions

Therefore, it is necessary to continue studying P. pentosaceus for further use. Thorough study of several P. pentosaceus strains should clarify the benefits and drawbacks in the future.

Effect of a Laminarin Rich Macroalgal Extract on the Caecal and Colonic Microbiota in the Post-Weaned Pig

Dietary supplementation with 300 ppm of a laminarin rich macroalgal extract reduces post-weaning intestinal dysfunction in pigs. A comprehensive analysis of the impact of laminarin on the intestinal microbiome during this period is essential to inform on the mode of action of this bioactivity. The objective of this study was to evaluate the effects of supplementing the diet of newly weaned pigs with 300 ppm of a laminarin rich extract, on animal performance, volatile fatty acids, and the intestinal microbiota using 16S rRNA gene sequencing. Pigs fed the laminarin-supplemented diet had higher average daily feed intake, growth rate, and body weight compared to pigs fed the control diet (p < 0.05). Pigs fed the laminarin-supplemented diet had reduced abundance of OTUs assigned to Enterobacteriaceae and increased abundance of OTUs assigned to the genus Prevotella (p < 0.05) compared to pigs fed the control diet. Enterobacteriaceae had negative relationships (p < 0.05) with average daily feed intake (ADFI), average daily gain (ADG), and butyric acid concentrations. In contrast, Prevotellaceae were positively correlated (p < 0.05) with ADFI, ADG, total VFA, acetic, propionic, butyric acids, and negatively correlated with isovaleric acid. Hence supplementation with a laminarin enriched extract potentially improves performance during the post-weaning period by promoting the proliferation of bacterial taxa such as Prevotella that favourably enhance nutrient digestion while reducing the load of potentially pathogenic bacterial taxa including Enterobacteriaceae.

Probiotic Properties of Lactobacillus brevis KU200019 and Synergistic Activity with Fructooligosaccharides in Antagonistic Activity against Foodborne Pathogens

This study aims to evaluate the probiotic properties of Lactobacillus brevis (L. brevis) KU200019 and the synergistic activity with prebiotics on antimicrobial activity, and the potential application as an adjunct culture in fermented dairy products. The commercial strain, L. brevis ATCC 14869 was used as reference strain. L. brevis KU200019 was showed higher viability in simulated gastric (99.38±0.21%) and bile (115.10±0.13%) conditions compared to reference strain. L. brevis KU200019 exhibited antimicrobial activity against various foodborne pathogens. The supplementation of fructooligosaccharides (FOS) enhanced viability of lactic acid bacteria (>8 Log CFU/mL) and antioxidant activity [2,2-diphenyl-2-picrylhydrazyl radical assay (DPPH) assay, 31.23±1.14%; 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assay, 38.82±1.46%] in fermented skim milk during refrigerated storage. L. brevis KU200019 was distinguished from the reference strain by its higher probiotic potential, antimicrobial activity, and higher antioxidant activity in fermented milk. Therefore, L. brevis KU200019 with FOS was demonstrated promising properties for further application in fermented dairy products with enhanced safety and quality.

Probiotic and Triticale Silage Fermentation Potential of Pediococcus pentosaceus and Lactobacillus brevis and Their Impacts on Pathogenic Bacteria

The purpose of this study was to identify potent lactic acid bacteria that could have a great impact on triticale silage fermentation at different moisture levels and determine their anti-bacterial activity and high probiotic potential. For this purpose, Pediococcus pentosaceus (TC48) and Lactobacillus brevis (TC50) were isolated from fermented triticale silage. The fermentation ability of these isolates in triticale powder was studied by an ensiling method. TC48 had higher ability to ferment silage powder by increasing the lactic acid content of silage than TC50. Extracellular supernatant (ECS) of TC48 and TC50 exhibited strong antibacterial effects (inhibition zone diameters: 18-28 mm) against tested cattle pathogenic bacteria with minimum inhibitory/ minimum bactericidal concentrations (MIC/MBC) values of 5.0-10 mg/mL and 10-20 mg/mL, respectively. Extracellular supernatant (ECS) of TC48 and TC50 showed antibacterial activities on E. coli, P. aeruoginosa, S. aureus and E. faecalis through destruction of membrane integrity as confirmed by decreased viability, and increased 260 nm absorbing material in culture filtrate of pathogenic bacteria exposed to ECS of both strains. TC48 and TC50 strains exhibited high tolerance to artificial gastric, duodenal and intestinal fluids. TC48 showed good hydrophobicity and auto-aggregations properties. TC48 and TC50 significantly co-aggregated with E. coli, P. aeruoginosa, S. aureus and E. faecalis in a time-dependent manner. In summary, all of the bacteria had a positive impact on at least one functional property of the silage during the fermentation process. However, the addition of P. pentosaceus (TC48) and L. brevis (TC50) yielded the greatest silage quality improvement, having high antibacterial and probiotic properties.

Characterization and Antibacterial Potential of Lactic Acid Bacterium Pediococcus pentosaceus 4I1 Isolated from Freshwater Fish Zacco koreanus

This study was undertaken to characterize a lactic acid bacterium 4I1, isolated from the freshwater fish, Zacco koreanus. Morphological, biochemical, and molecular characterization of 4I1 revealed it to be Pediococcus pentosaceus 4I1. The cell free supernatant (CFS) of P. pentosaceus 4I1 exhibited significant (p < 0.05) antibacterial effects (inhibition zone diameters: 16.5-20.4 mm) against tested foodborne pathogenic bacteria with MIC and MBC values of 250-500 and 500-1,000 μg/mL, respectively. Further, antibacterial action of CFS of P. pentosaceus 4I1 against two selected bacteria Staphylococcus aureus KCTC-1621 and Escherichia coli O157:H7 was determined in subsequent assays. The CFS of P. pentosaceus 4I1 revealed its antibacterial action against S. aureus KCTC-1621 and E. coli O157:H7 on membrane integrity as confirmed by a reduction in cell viability, increased potassium ion release (900 and 800 mmol/L), reduced absorption at 260-nm (3.99 and 3.77 OD), and increased relative electrical conductivity (9.9 and 9.7%), respectively. Gas chromatography-mass spectrometry (GC-MS) analysis of the CFS of P. pentosaceus 4I1 resulted in the identification of seven major compounds, which included amino acids, fatty acids and organic acids. Scanning electron microscopic-based morphological analysis further confirmed the antibacterial effect of CFS of P. pentosaceus 4I1 against S. aureus KCTC-1621 and E. coli O157:H7. In addition, the CFS of P. Pentosaceus 4I1 displayed potent inhibitory effects on biofilms formation by S. aureus KCTC-1621 and E. coli O157:H7. The study indicates the CFS of P. pentosaceus 4I1 offers an alternative means of controlling foodborne pathogens.