Characterization, Cytotoxic Analysis and Action Mechanism of Antilisterial Bacteriocin Produced by Lactobacillus plantarum Isolated from Cheddar Cheese

A novel bacteriocin against methicillin-resistant Staphylococcus aureus, purified from Lactiplantibacillus plantarum ZFM9

A novel bacteriocin, plantaricin ZFM9, was purified from Lactiplantibacillus plantarum ZFM9 using a combination of ammonium sulfate precipitation, XAD-2 macroporous resin, Sephadex G-50, Sephadex LH-20, and reversed-phase high performance liquid chromatography. The molecular mass of plantaricin ZFM9 was 1151.606 Da, and the purity was 98.3%. Plantaricin ZFM9 has thermal stability (95.6% retention at 120 °C for 30 min), pH stability (pH ≤ 5), and sensitivity to the pepsin, trypsin, papain, and proteinase K. Plantaricin ZFM9 exhibited broad-spectrum antimicrobial activity and notably inhibit methicillin-resistant Staphylococcus aureus D48 (MRSA). According to the results of electron microscopy and fluorescence leakage assay, it was found that plantaricin ZFM9 caused damage to the cells membrane and leakage of the contents of S. aureus D48. In addition, Lipid II was not the anti-MRSA target of plantaricin ZFM9. This study underscores the potential of plantaricin ZFM9 for applications in the food field and biopharmaceuticals against MRSA infection.

Bactericidal and non-cytotoxic activity of bacteriocin produced by Lacticaseibacillus paracasei F9-02 and evaluation of its tolerance to various physico-chemical conditions

This study aims to explore novel lactic acid bacteria (LAB) from breast-fed infants' faeces towards characterizing their antimicrobial compound, bacteriocin. The LAB, Lacticaseibacillus paracasei F9-02 showed strong antimicrobial activity against clinical pathogens. Their proteinaceous nature was confirmed as the activity was completely abolished when treated with proteinaceous enzymes and retained during neutral pH and catalase treatment. The purified bacteriocin showed antimicrobial activity at the minimum inhibitory concentration (MIC) value of 7.56 μg/ml against vancomycin-resistant Enterococcus sp. [vancomycin-resistant enterococcal (VRE)], and methicillin-resistant Staphylococcus aureus (MRSA), 15.13 μg/ml against Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella enterica subsp. enterica serotype typhi and 30.25 μg/ml against Shigella flexneri. Present study also proved the bactericidal, non-cytotoxic and non-hemolytic nature of bacteriocin. Additionally, bacteriocin retained their stability under various physico-chemical conditions, broad range of pH (2-10), temperature (40-121°C), enzymes (amylase, lipase and lysozyme), surfactants [Tween-20, 80, 100 and sodium dodecyl sulfate (SDS)], metal ions (CaCl2 , FeSO4 , ZnSO4 , MgSO4 , MnSO4 , CuCl2 ) and NaCl (2%-8%). The molecular weight of bacteriocin (~28 kDa) was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), functional and active groups were assessed by Fourier Transform-Infrared (FT-IR). To our knowledge, this is the first study reporting L. paracasei from breast-fed infants' faeces and assessing their antimicrobial compound, bacteriocin. The study results furnish the essential features to confirm the therapeutic potential of L. paracasei F9-02 bacteriocin.

Purification and characterization of bacteriocin produced by a strain of Lacticaseibacillus rhamnosus ZFM216

The recent surge in demand for natural preservatives has ushered in a new era of research into novel bacteriocins capable of effectively combating food-borne infections. In this study, the bacteriocin from Lacticaseibacillus rhamnosus ZFM216, which has a molecular mass of 11851.9 Da, was purified using macroporous resin, gel chromatography, and reversed-phase high performance liquid chromatography. This bacteriocin could inhibit both Gram-positive and Gram-negative bacteria. It had a strong inhibitory effect on Staphylococcus aureus D48 with minimum inhibitory concentration values of 1.75 μM. Bacteriocin ZFM216 was heat stable and showed pH stability under weakly acidic conditions. It was sensitive to pepsin, proteinase K and trypsin. Electron microscopy results showed that when treated with bacteriocin ZFM216, S. aureus D48 was severely deformed, the cell structure was obviously changed, and the intracellular electrolyte leaked to the outside of the cell. Bacteriocin ZFM216 caused the ATP level of the indicator to decrease, the conductivity to sharply increase, and the transmembrane potential difference (ΔΨ) to instantaneously decrease. This research formed the basis for further development and utilization of bacteriocin ZFM216 which has potential in the food industry.

Antimicrobial, anti-biofilm, antioxidant and cytotoxic effects of bacteriocin by Lactococcus lactis strain CH3 isolated from fermented dairy products-An in vitro and in silico approach

The current study aimed to screen bacteriocin producing LAB from different dairy products and evaluation of their biological properties. Initially, 12 (4-chess, 4-curd, and 4-yohurt) LAB species were isolated and only 4 isolates alone were selected based on their clear yellow halo zone around the colonies in the selective medium. The selected 4 isolates were identified based on their morphological and biochemical characteristics. Among them, the strain CH3 have showed better antimicrobial effects on selected human pathogens. The isolated strain CH3 were further identified as Lactococcus lactis strain CH3 (MZ636710) by SEM imaging and 16 s rRNA molecular sequencing. Bacteriocin was extracted from L. lactis strain CH3 and partially purified using 60 % ammonium sulphate and then completely purified by G-50 column chromatography. The purified bacteriocin showed a specific activity of 5859.37 AU/mg in 24.7 % of recovery and 10.9-fold purification. The molecular weight of bacteriocin was 3.5 kDa as observed in SDS-PAGE. The bacteriocin showed sensitivity to proteolytic enzymes and resistance to high temperature, wide range of pH, organic solvents and detergents. FT-IR spectral studies of bacteriocin detected the existence of OH/NH-stretching, CH, and COC and CO bonds. NMR spectrum showed one doublet and 4 various singlet peaks at different ppm, indicating the occurrence of six amino acids in the structure of purified bacteriocin. The purified bacteriocin have shown stronger antimicrobial and anti-biofilm activity against selected human pathogens at 100 μg/mL. SEM showed the evidence of structural deformation and loss of membrane integrity of bacterial cells treated with bacteriocin. Bacteriocin exhibited greater DPPH radical scavenging potential with an EC₅₀ value of 12.5 μg/mL. Bacteriocin have not shown significant toxicity on normal human dermal fibroblast (NHDF) cells (83.2 % at 100 μg/ mL). Furthermore, in silico studies using molecular modeling and docking were performed to know the proteins involved in antimicrobial action. The results suggests that bacteriocin could be an alternative to combat AMR pathogens and more suitable for food and dairy industries to preserve food without contamination.

Thurincin H Is a Nonhemolytic Bacteriocin of Bacillus thuringiensis with Potential for Applied Use

Thurincin H, a bacteriocin produced by Bacillus thuringiensis, exhibits antibacterial activity against Gram-positive and Gram-negative bacteria. While much is known about its expression and antimicrobial spectrum, its hemolytic property has yet to be established. In this study, thurincin H was produced in a plasmid-free acrystalliferous strain of B. thuringiensis (Bt Cry^-B) that naturally lacked antimicrobial and hemolytic activities. When grown in Tryptic Soy Broth (TSB), the bacteriocin's maximal production in Bt Cry^-B harboring the thurincin H genetic cluster (Bt Cry^-B/pThur) was observed at 24 h. Thurincin H was purified as a sole peptide of ~5 kDa using three purification steps, i.e., salt precipitation, ultrafiltration, and gel filtration chromatography. The bacteriocin showed inhibitory activity against B. cereus (5631 U), Bt Cry^-B (8827 U), E. faecium wild type (11,197 U), and E. faecium ATCC 19,434 (6950 U), but not against Bt Cry^-B/pThurH and Bt Cry^-B/pThurHΔThnA. In addition, a minimum inhibitory concentration (MIC) of 5.0 μg/mL against B. cereus 183 was observed. In silico predictions suggested that thuricin H lacks hemolytic activity, which was validated in vitro using 4 × the MIC, i.e., 20 μg/ml. Our data lay a foundation for the potential safe use of thurincin H as an antibacterial peptide for medical use, in food products, and for expression in probiotic bacteria.

Bacteriocins Produced by LAB Isolated from Cheeses within the Period 2009-2021: a Review

A survey is presented concerning original research articles published in well-reputed scientific journals on the isolation of lactic acid bacteria (LAB) from cheeses worldwide, where researchers evaluated the bacteriocin production by such isolates in searching for novel functional peptides that can exhibit potential for biotechnological applications. Seventy-one articles were published in the period of study, with contributions being American (45%), Asiatic (28%), and European (21%), being Brazil-USA-Mexico, Turkey-China, and France-Italy the countries that contributed the most for each said continent, respectively. Most of the isolated LAB belong to the genera Enterococcus (35%), Lactobacillus (30%), Lactococcus (14%), and Pediococcus (10%), coming from soft (64%), hard (27%), and semi-hard (9%) cheeses, predominantly. Also, scholars focused mainly on the food biopreservation (81%) and pharmaceutical field (18%) potential applications.

Antimicrobial activity and cytotoxicity trait of a bioactive peptide purified from Lactococcus garvieae subsp. bovis BSN307T

A bioactive peptide of 8595 Da was purified from the cell free supernatant of Lactococcus garvieae subsp. bovis BSN307^T . MALDI MS/MS peptide mapping and the data base search displayed no significant similarity to any reported antimicrobial peptide of LAB. This peptide at a dose concentration of 200 µg ml^-1 inhibited the growth of both Gram-positive and Gram-negative bacteria by 58-89% and a dose of 500 µg ml^-1 scavenged 50% of DPPH-free radicals generated. Interestingly, cytotoxicity assay demonstrated that 17 µg ml^-1 of peptide selectively inhibited 50% proliferation of mammalian cancer cell lines HeLa and MCF-7 whereas normal H9c2 cells remained unaffected. Fluorescent microscopic analysis after DAPI nuclear staining of HeLa cells showed characteristics of apoptosis and activation of caspase-3 was ascertained by caspase-3 fluorescence assay.