Purification, amino acid sequence, and characterization of bacteriocin GA15, a novel class IIa bacteriocin secreted by Lactiplantibacillus plantarum GCNRC_GA15

A Review on Bacteriocin Extraction Techniques from Lactic Acid Bacteria

Lactic acid bacteria (LAB) are widely known for the production of secondary metabolites such as organic acids and other bioactive compounds such as bacteriocins. Finding a broad application in food and healthcare, bacteriocins have received increased attention due to their inherent antimicrobial properties. However, the extraction of bacteriocins is often plagued with low yields due to the complexity of the extraction processes and the diversity of bacteriocins themselves. Here, we review the current knowledge related to bacteriocin extraction on the different extraction techniques for isolating bacteriocins from LAB. The advantages and disadvantages of each technique will also be critically appraised, taking into account factors such as extraction efficiency, scalability and cost-effectiveness. This review aims to guide researchers and professionals in selecting the most suitable approach for bacteriocin extraction from LAB by illuminating the respective advantages and limitations of various extraction techniques.

Current status and potential of bacteriocin-producing lactic acid bacteria applied in the food industry

Lactic acid bacteria (LAB) have been widely applied in the food industry and have brought many beneficial effects on food products, and some of those benefits are related to their metabolic product. Bacteriocins produced by LAB have attracted the attentions for application in the food industry as natural food bio-preservatives because of their antimicrobial activity against the food spoilage and pathogenic bacteria. With the increasing demands of consumers for more healthier food and investigations on natural food preservatives, the bioactivity of bacteriocins allows them to give the application values to the bacteriocin-producing LAB. Accordingly, the capacity of LAB to produce bacteriocin in the aspects of classifications, mode of action, biosynthesis mechanisms are introduced, which leads to further consideration of the current status and potential values of bacteriocin-producing LAB applied in the food industry. The comparation of guidelines of LAB and bacteriocins for food application are also proposed for better understanding their practical application promising. This review will be helpful for current and future researches on the application of bacteriocin-producing LAB in the food industry.

Physicochemical and sensory characterization of functional synbiotic Labneh fortified with the bacteriocin-producing Lactiplantibacillus plantarum strain GA7 and nano-encapsulated Tirmania pinoyi extract

BACKGROUND

Functional foods and dairy products are gaining global attention due to their nutritional value and health-promoting characteristics. Lactic acid bacteria (LAB) are one of the promising components included in these products, thanks to their probiotic properties and ability to produce bioactive compounds such as bacteriocins. On the other hand, ectomycorrhizal wild mushrooms (truffles) are known for their ethnomycological importance. Hence, we aimed to develop a functional dairy product using a bacteriocin-producing LAB isolate that has probiotic potentials together with the bioactive extract of a truffle mushroom.

RESULTS

Screening for bacteriocin-producing LAB led to the selection of four safe isolates that also showed promising probiotic potentials. Isolate No. 7 was selected due to its wider antimicrobial spectrum and was identified as Lactiplantibacillus plantarum strain GA7. Out of resulting bands from Tricine SDS-PAGE analysis, a band (its molecular mass was approximately 7 kDa) exhibited antimicrobial activity. Amino acid sequencing of this active band detected 62 amino acid residues with 100% identity to plantaricin ASM1 bacteriocin. Simultaneously, an ethyl acetate extract was prepared from a truffle sample identified as Tirmania pinoyi. Safety of this truffle was confirmed and its extract exerted promising antioxidant and hypocholesterolemic activity. Prepared functional dairy products (Labneh) fortified with L. plantarum GA7 and nano-encapsulated T. pinoyi extract exhibited superior physicochemical, sensory and antioxidant properties compared to control. Moreover, an increase in probiotic count was observed in presence of T. pinoyi extract. Furthermore, prepared Labneh using the bacteriocin-producing L. plantarum GA7 and nano-encapsulated T. pinoyi extract remained unspoiled for over 60 days, compared to control, which spoiled after 21 days.

CONCLUSION

Besides improving Labneh physicochemical, sensory and antioxidant properties, the presence of the bacteriocin-producing L. plantarum GA7 has contributed in significantly extending its shelf life, while T. pinoyi extract showed prebiotic influence on probiotic count. As far as we know this is the first study describing production of a functional synbiotic dairy product fortified with bacteriocin-producing probiotic LAB and bioactive T. pinoyi truffle extract.

Potential and application of tandem mass spectrometry (MS/MS) in the analysis and identification of novel bacteriocins: a review

Bacteriocins are antimicrobial peptides synthesised ribosomally by Gram-positive or Gram-negative bacteria to gain a competitive advantage. The majority of bacteriocins are derived from Gram-positive bacteria, with lactic acid bacteria being the most common source. Because they are considered ‘natural’, there is currently significant development of bacteriocins for application as food preservative agents. As a preservative agent, bacteriocin activity is highly dependent on purity, down to the amino acid profile and sequence. Therefore, bacteriocin identification is important. Currently, MS is a cutting-edge tool in bacteriocin identification. This method has high selectivity, sensitivity and resolution. To the best of our knowledge, systematic reviews focusing on the application of MS for bacteriocin identification are currently limited. In light of this, the objective of this study is to provide a comprehensive review and summary of MS technologies in bacteriocin research, with a particular focus on the discovery and characterisation of novel sources of bacteriocin. Additionally, studies related to the discovery of bacteriocins from various sources, their role as antimicrobial agents, and their synthesis are emphasised. Thus, this study presents a comprehensive analysis of the advantages, limitations, and future perspectives of the methods employed.

Potential of enterocin from Enterococcus durans MF5 in controlling Listeria species

This research paper presents the characterization of an enterocin-producing Enterococcus durans MF5 isolate and the determination of the in vitro antilisterial activity of enterocin produced by this isolate, named Ent-MF5. PCR-based screening for bacteriocin biosynthetic genes revealed that E. durans MF5 harbors multiple enterocin-encoding genes (ent A, B, P and X), classified as class II bacteriocins and enterocin-P of Enterococcus faecium (sharing up to 99% similarity at the genetic level). E. durans MF5 is sensitive to eight clinically important antibiotics and does not possess cytolysin activator -cylA, gelatinase -gelE and hyaluronidase -hylA virulence genes. The antilisterial activity of Ent-MF5 was abolished by trypsin, α-chymotrypsin, protease and proteinase-K. Ent-MF5 showed thermal and pH stability. In addition, the activity of Ent-MF5 was unaffected in the presence of various surfactants (1% SDS, Triton X-100, Tween 20, and Tween 80). Ent-MF5 exhibited antimicrobial activity against Listeria monocytogenes, Listeria innocua, Listeria ivanovii and Listeria seeligeri at concentrations as low as 0.13 μg/ml. Ent-MF5 had a bactericidal effect against L. monocytogenes with a significant reduction in surviving cells at concentrations equal to or greater than 0.13 μg/ml. A 75-100% reduction in L. monocytogenes growth and bactericidal effect determined by CFU counts was observed following treatment with Ent-MF5 at 4.47 μg/ml at time points starting at 2 and 4 h, respectively. Ent-MF5 action is associated with Listeria cell membrane damage, as observed by flow cytometry and fluorescence microscopy. Thus, the effective antilisterial activity and stability of Ent-MF5 presents promising perspectives for application as biopreservatives in the food industry.

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.

Growth Control of Listeria monocytogenes in Raw Sausage via Bacteriocin-Producing Leuconostoc carnosum DH25

The current study addresses the critical issue of Listeria monocytogenes growth in raw sausage/meat products leading to human infections, most commonly listeriosis, which is known for its high fatality rate. This research focuses on the isolation, identification, and screening of lactic acid bacteria from various meat and fish products in Switzerland. In total, 274 lactic acid bacteria strains were isolated from 30 different products and were screened for their ability to inhibit Listeria monocytogenes growth, with 51 isolates demonstrating anti-Listeria activity at 8 °C, 15 °C, 25 °C, and 37 °C. Further experiments, using a meat model and a raw sausage challenge test, demonstrated that Leuconostoc carnosum DH25 significantly inhibited Listeria monocytogenes growth during the ripening and storage of the tested meat/sausage. This inhibitory effect was found to be attributed to the bacteriocins produced by Leuconostoc carnosum DH25 rather than factors like pH or water activity. The stability of the anti-Listeria substances was examined, revealing their resistance to temperature and pH changes, making Leuconostoc carnosum DH25 a promising protective culture for raw sausages. The genome sequencing of this strain confirms its safety, with no antibiotic resistance genes or virulence factors detected, and reveals the presence of the structural genes for the production of the bacteriocin LeucocinB-Ta11a. This study underscores the potential of LAB strains and their bacteriocins as effective tools for enhancing food safety and preventing Listeria monocytogenes growth in meat products, offering valuable insights into biocontrol strategies in the food industry.

Gene expression and molecular characterization of recombinant subtilisin from Bacillus subtilis with antibacterial, antioxidant and anticancer properties

This study investigated the multifunctional attributes such as, antibacterial, antioxidant and anticancer potential of recombinant subtilisin. A codon-optimized subtilisin gene was synthesized from Bacillus subtilis and was successfully transformed into E. coli DH5α cells which was further induced for high level expression in E. coli BL21 (DE3). An affinity purified ~40 kDa recombinant subtilisin was obtained that revealed to be highly alkali-thermostable based on the thermodynamic parameters. The kinetic parameters were deduced that indicated higher affinity of N-Suc-F-A-A-F-pNA substrate towards subtilisin. Recombinant subtilisin demonstrated strong antibacterial activity against several pathogens and showed minimum inhibitory concentration of 0.06 μg/mL against B. licheniformis and also revealed high stability under the influence of several biochemical factors. It also displayed antioxidant potential in a dose dependent manner and exhibited cell cytotoxicity against A549 and MCF-7 cancerous cell lines with IC50 of 5 μM and 12 μM respectively. The identity of recombinant subtilisin was established by MALDI-TOF mass spectrum depicting desired mass peaks and N-terminal sequence as MRSK by MALDI-TOF-MS. The deduced N- terminal amino acid sequence by Edman degradation revealed high sequence similarity with subtilisins from Bacillus strains. The structural and functional analysis of recombinant antibacterial subtilisin was elucidated by Raman, circular dichroism and nuclear magnetic resonance spectroscopy and thermogravimetric analysis. The results contribute to the development of highly efficient subtilisin with enhanced catalytic properties making it a promising candidate for therapeutic applications in healthcare industries.

Potential Impact of Combined Inhibition by Bacteriocins and Chemical Substances of Foodborne Pathogenic and Spoilage Bacteria: A Review

In recent years, food safety caused by foodborne pathogens and spoilage bacteria has become a major public health problem worldwide. Bacteriocins are a kind of antibacterial peptide synthesized by microbial ribosomes, and are widely used as food preservatives. However, when used individually bacteriocins may have limitations such as high cost of isolation and purification, narrow inhibitory spectrum, easy degradation by enzymes, and vulnerability to complex food environments. Numerous studies have demonstrated that co-treatment with bacteriocins and a variety of chemical substances can have synergistic antibacterial effects on spoilage microorganisms and foodborne pathogens, effectively prolonging the shelf life of food and ensuring food safety. Therefore, this paper systematically summarizes the synergistic bacteriostatic strategies of bacteriocins in combination with chemical substances such as essential oils, plant extracts, and organic acids. The impacts of bacteriocins when used individually and in combination with other chemical substances on different food substrates are clarified, and bacteriocin-chemical substance compositions that enhance antibacterial effectiveness and reduce the potential negative effects of chemical preservatives are highlighted and discussed. Combined treatments involving bacteriocins and different kinds of chemical substances are expected to be a promising new antibacterial method and to become widely used in both the food industry and biological medicine.

Quorum sensing-mediated microbial interactions: Mechanisms, applications, challenges and perspectives

Microbial community in natural or artificial environments playes critical roles in substance cycles, products synthesis and species evolution. Although microbial community structures have been revealed via culture-dependent and culture-independent approaches, the hidden forces driving the microbial community are rarely systematically discussed. As a mode of cell-to-cell communication that modifies microbial interactions, quorum sensing can regulate biofilm formation, public goods secretion, and antimicrobial substances synthesis, directly or indirectly influencing microbial community to adapt to the changing environment. Therefore, the current review focuses on microbial community in the different habitats from the quorum sensing perspective. Firstly, the definition and classification of quorum sensing were simply introduced. Subsequently, the relationships between quorum sensing and microbial interactions were deeply explored. The latest progressives regarding the applications of quorum sensing in wastewater treatment, human health, food fermentation, and synthetic biology were summarized in detail. Finally, the bottlenecks and outlooks of quorum sensing driving microbial community were adequately discussed. To our knowledge, this current review is the first to reveal the driving force of microbial community from the quorum sensing perspective. Hopefully, this review provides a theoretical basis for developing effective and convenient approaches to control the microbial community with quorum sensing approaches.