Separation of lactobacilli bacteriocins from fermented broths using membranes

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.

A novel antimicrobial peptide YS12 isolated from Bacillus velezensis CBSYS12 exerts anti-biofilm properties against drug-resistant bacteria

Nowadays, the abuse of antibiotics has led to the rise of multi-drug-resistant bacteria. Antimicrobial peptides (AMPs), with broad-spectrum antimicrobial activity have attracted considerable attention as possible alternatives to traditional antibiotics. In this work, we aimed to evaluate the antimicrobial and anti-biofilm activity of an antimicrobial peptide designed as YS12 derived from Bacillus velezensis CBSYS12. The strain CBSYS12 was isolated from Korean food kimchi and purified followed by ultrafiltration and sequential chromatographic methodology. Hereafter, Tricine SDS-PAGE revealed a single protein band of around 3.3 kDa that was further confirmed in situ inhibitory activity of the gel. A similar molecular weight (~ 3348.4 Da) protein also appeared in MALDI-TOF confirming the purity and homogeneity of peptide YS12. Intriguingly, YS12 revealed a strong antimicrobial activity with a minimum inhibitory concentration (MIC) value ranging from 6 to 12 μg/ml for both Gram-positive and Gram-negative bacteria, such as E. coli, P. aeruginosa, MRSA 4-5, VRE 82, and M. smegmatis. We also determined the mode of action of the peptide against pathogenic microorganisms using different fluorescent dyes. In addition, the anti-biofilm assay demonstrated that peptide YS12 was able to inhibit biofilm formation  around 80% for both bacterial strains E. coli and P. aeruginosa at 80 µg/ml. Notably, YS12 exhibited a greater biofilm eradication activity than commercial antibiotics. In summary, our study proposed that peptide YS12 may be used as a promising therapeutic agent to overcome drug and biofilm-related infections.

Inhibition Activity of Plantaricin Q7 Produced by Lactobacillus plantarum Q7 against Listeria monocytogenes and Its Biofilm

Plantaricin Q7 is a broad-spectrum antimicrobial peptide produced by Lactobacillus plantarum Q7. The effects of plantaricin Q7 on Listeria monocytogenes and its biofilm were investigated. The results showed that plantaricin Q7 changed the cell membrane permeability and integrity of Listeria monocytogenes significantly. The extracellular lactate dehydrogenase activity increased from 156.74 U/L to 497.62 U/L, and the K+ concentration was increased rapidly from 0.02 g/L to 0.09 g/L. Furthermore, the flagellum motility of Listeria monocytogenes reduced and the relative adhesion rate decreased about 30% after treatment with plantaricin Q7. Meanwhile, the morphology and structure of Listeria monocytogenes cell and biofilm were damaged. These findings suggested that plantaricin Q7 exhibited significant inhibitory effects on not only Listeria monocytogenes cell but also its biofilm, which might be used as a natural and effective biological preservative for food storage.

Partial Purification and Characterization of Bacteriocin-Like Inhibitory Substances Produced by Streptomyces sp. Isolated from the Gut of Chanos chanos

Bacteriocin-like inhibitory substances (BLIS) have sparked great interest because of their promising use in food as natural antimicrobial agents. In this work, six Streptomyces isolates obtained from the gut of Chanos chanos demonstrated their ability to produce extracellular metabolites with inhibitory activity against Salmonella enterica serovar Typhimurium, Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus. Exposure of the extracellular metabolites to proteolytic enzymes (i.e., proteinase-K, trypsin, and pepsin) revealed high sensitivity and confirmed their proteinaceous nature. The metabolites were stable at high temperatures (up to 100°C for 30 min) and a wide range of pH (pH 2.0–7.0). Fractionation of the crude BLIS by filtration yielded three fractions based on molecular weight: <3 kDa, 3–10 kDa, and >10 kDa. Analysis of the antibacterial activity of these fractions showed increased specific activity, especially in the fraction with a molecular weight (MW) of <3 kDa, relative to the crude sample. The fraction with MW < 3 kDa had minimum inhibitory and bactericidal concentrations in ranges 0.04–0.62 mg·mL⁻¹ and 0.08–1.25 mg·mL⁻¹, respectively. This fraction also showed better temperature and pH stability compared with crude BLIS. Brine shrimp toxicity assay revealed that this fraction has moderate toxicity with a 50% lethal concentration of 226.975 μg·mL⁻¹ (i.e., moderate toxicity) to Artemia salina. Identification of the peptide sequences of this fraction by liquid chromatography–tandem mass spectrometry yielded 130 proteins with retention times of 15.21–19.57 min. Eleven proteins with MWs of 1345.66–2908.35 Da and composed of less than 30 amino acid residues with high hydrophobicity (15.34–26.22 kcal·mol⁻¹) appeared to be responsible for the antibacterial activity of the fraction. This study revealed the potential application of BLIS from Streptomyces, especially BLIS SCA-8, as antibacterial agents.

Overview of Global Trends in Classification, Methods of Preparation and Application of Bacteriocins

This paper summarizes information about the division of bacteriocins into classes (Gram-negative bacteria, Gram-positive bacteria, and archaea). Methods for producing bacteriocins have been studied. It is known that bacteriocins, most successfully used today are products of secondary metabolism of lactic acid bacteria. It is established that the main method of bacteriocin research is PCR analysis, which makes it possible to quickly and easily identify the presence of bacteriocin encoding genes. The mechanism of cytotoxic action of bacteriocins has been studied. It is proved that the study of cytotoxic (antitumor) activity in laboratory conditions will lead to the clinical use of bacteriocins for cancer treatment in the near future. It is established that the incorporation of bacteriocins into nanoparticles and targeted delivery to areas of infection may soon become an effective treatment method. The delivery of bacteriocins in a concentrated form, such as encapsulated in nanoparticles, will increase their effectiveness and minimize potential toxic side effects. The analysis of publications on this topic confirmed that diverse research on bacteriocins is relevant.

Gram-positive bacteriocins: usage as antimicrobial agents in veterinary medicine

Antimicrobial resistance is a worldwide spread phenomenon that affects both human and veterinary medicine. This issue has led to a "One Health" approach in order to coordinate efforts and set back the development of drug-resistant microbes. In the search for alternatives therapies, bacteriocins or antimicrobial peptides have proven to be effective both in vitro and in vivo for multiples pathogens, even those resistant to many classic antibiotics. Gram-positive bacteriocins have been the most studied to the present. The use of bacteriocins as therapeutically active molecules is limited mainly due to difficulties in production, purification, delivery systems and regulatory approvals. To overcome some of these limitations, biotechnological and nanotechnological approaches are evaluated. Bacteriocins proved to be a good complement for conventional antibiotics therapy. Antimicrobial peptides are nowadays included in the veterinary products such as udder disinfectant for dairy cattle and dermatological medicated wipe for topical use on dogs, cats, and horses. But there are other potential uses to explore in the veterinary field for both companion and production animals.

Purification of a Bacteriocin-Like Inhibitory Substance Derived from Pediococcus acidilactici Kp10 by an Aqueous Micellar Two-Phase System

Aqueous micellar two-phase system (AMTPS) is an extractive technique of biomolecule, where it is based on the differential partitioning behavior of biomolecule between a micelle-rich and a micelle-poor phase. In this study, an AMTPS composed of a nonionic surfactant, Triton X-100 (TX-100) was used for purifying a bacteriocin-like inhibitory substance (BLIS) derived from Pediococcus acidilactici Kp10. The influences of the surfactant concentration and the effect of additives on the partitioning behavior and activity yield of the BLIS were investigated. The obtained coexistence curves showed that the mixtures of solutions composed of different surfactant concentrations (5-30% w/w) and 50% w/w crude load were able to separate into two phases at temperatures of above 60 °C. The optimum conditions for BLIS partitioning using the TX-100-based AMTPS were: TX-100 concentration of 22.5% w/w, CFCS load of 50% w/w, incubation time of 30 min at 75 °C, and back-extraction using acetone precipitation. This optimal partitioning resulted in an activity yield of 64.3% and a purification factor of 5.8. Moreover, the addition of several additives, such as sorbitol, KCl, dioctyl sulfosuccinate sodium salt, and Coomassie® Brilliant Blue, demonstrated no improvement in the BLIS separation, except for Amberlite® resin XAD-4, where the activity yield was improved to 70.3% but the purification factor was reduced to 2.3. Results from this study have demonstrated the potential and applicability of TX-100-based AMTPS as a primary recovery method for the BLIS from a complex fermentation broth of P. acidilactici Kp10. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2719, 2019.

Nanotechnology: A Valuable Strategy to Improve Bacteriocin Formulations

Bacteriocins are proteinaceous antibacterial compounds, produced by diverse bacteria, which have been successfully used as: (i) food biopreservative; (ii) anti-biofilm agents; and (iii) additives or alternatives to the currently existing antibiotics, to minimize the risk of emergence of resistant strains. However, there are several limitations that challenge the use of bacteriocins as biopreservatives/antibacterial agents. One of the most promising avenues to overcome these limitations is the use of nanoformulations. This review highlights the practical difficulties with using bacteriocins to control pathogenic microorganisms, and provides an overview on the role of nanotechnology in improving the antimicrobial activity and the physicochemical properties of these peptides.