Bacteriocin Activity Research Articles

Evaluation of the probiotic ability of Cellulolytic Bacillus subtilis SBMP4 (FSP20) isolated from waste-dump site in FIIRO, Lagos Nigeria

BACKGROUND: Current invention in the field of biotechnology includes research into the probiotic potentials of enzyme-producing bacteria species. OBJECTIVE: This study evaluated the probiotic ability of cellulolytic Bacillus subtilis SBMP4 isolated from waste dump site. METHODS: Isolated Bacillus species was screened for cellulolytic ability on carboxyl methylcellulose agar (CMCA), and hydrolysis efficiency was calculated. Probiotic ability of cellulolytic Bacillus species was carried out as follows: pathogenic potentials, bacteriocin producing ability, antibiotic susceptibility testing, gastric acid, and bile tolerance. Molecular identification was done by means of 16S rRNA gene sequencing, blast search analysis and phylogenetic analysis. RESULTS: Zone of clearance of 30 ± 2.08 mm on CMCA with hydrolysis efficiency of 114 % depicted the isolate’s cellulolytic potential. Bacillus subtilis SBMP4 showed γ-hemolytic phenotype with negative lecithinase activity. Antibacterial activity of bacteriocin observed against Staphylococcus aureus ATCC 25923 reference culture, had maximum inhibition zone of 14±1.0 mm at 72 hour of incubation. Substantial susceptibility towards 9 out of 10 commonly used antibiotics further depicted the isolate’s probiotic ability. Bacillus subtilis SBMP4 exhibited good gastric acid tolerance (pH 2.5) of 5.857 Log cycle/ml and good tolerance to 5 % and 10 % bile salt concentrations with 6.134 and 6.301 Log cycle/ml of viable bacteria cells. Molecular identification of the selected bacteria species revealed it to be Bacillus subtilis SBMP4 with RefSeq accession number NR_118383, showing maximum sequence similarity of 98%. CONCLUSION: Cellulolytic Bacillus subtilis SBMP4 possesses good probiotic ability and has the potentials of being applied as additive in livestock feeding to enhance overall productivity. KEYWORDS: Cellulolytic, Probiotic, CelA gene, Bacteriocin, Bacillus subtilis

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

SummaryBacteriocins 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.

Anti-biofilm and antibacterial effect of bacteriocin derived from Lactobacillus plantarum on the multidrug-resistant Acinetobacter baumannii

This research examines the impact of bacteriocin derived from Lactobacillus plantarum PTCC 1745 on the biofilm formations of A. baumannii isolates. Bacteriocin derived from L. plantarum PTCC 1745 was obtained through ammonium sulfate precipitation, cation-exchange chromatography, and reversed-phase high-performance liquid chromatography (RP-HPLC). Testing for bacteriocin susceptibility has been conducted using the broth dilution method. The anti-biofilm activity of bacteriocin was evaluated using a microtiter plate method. Quantitative real-time PCR assay evaluated bap gene expression in bacteriocin-treated cells. According to SDS-PAGE, bacteriocin from L. plantarum has a 25-kDa apparent molecular weight. The MICs of bacteriocin ranged from 30 to 120 μg/mL, while the MBCs varied between 60 and 120 μg/mL. Compared to the non-treated group, strains bacteriocin-treated isolates had 59 % less ability to form biofilm. The mean relative expression of the bap gene among the MDR A. baumannii isolates decreased by 52 % compared to the untreated control. This study demonstrated that bacteriocin derived from L. plantarum PTCC 1745 had antibacterial and antibiofilm activity against MDR A. baumannii isolates.

MOLECULAR CHARACTERIZATION AND DETERMINATION OF ANTIMICROBIAL POTENTIAL OF PROBIOTIC BACTERIA ISOLATED FROM TRADITIONAL DAIRY AND COMMERCIAL PRODUCTS

The objective of the present study was to isolate, identify, and characterize probiotic Lactic acid bacterial strains from traditional dairy and commercial products and determine their antagonistic activity against pathogenic bacteria. Fifty-five lactic acid bacterial (LAB) strains were isolated, and fifteen strains were selected based on probiotic potential after that antimicrobial activity was measured against bacterial pathogens. Among fifteen isolates, five isolates showed good (above 15 mm zone) antimicrobial activities against the tested pathogenic strains of humans. After the preliminary antimicrobial activity, the best five isolates were selected for the production of different antibacterial compounds such as bacteriocin, hydrogen peroxide, and organic acid. Two isolates showed bacteriocin production and one isolate gave maximum bacteriocin activity against most pathogens and was further identified as Enterococcus faecalis JY32 using 16 S rRNA sequencing. The study reveals that in comparison to commercial products, traditional products of dairy could be an alternative and readily available resource for probiotic bacteria with interesting functional characteristics.

Expression of Caseicin from Lacticaseibacillus casei and Lacticaseibacillus zeae Provides Insight into Antilisterial Class IIa Bacteriocins.

In this study, an in silico screening approach was employed to mine potential bacteriocin clusters in genome-sequenced isolates of Lacticaseibacillus zeae UD 2202 and Lacticaseibacillus casei UD 1001. Two putative undescribed bacteriocin gene clusters (Cas1 and Cas2) closely related to genes encoding class IIa bacteriocins were identified. No bacteriocin activity was recorded when cell-free supernatants of strains UD 2202 and UD 1001 were tested against Listeria monocytogenes. Genes encoding caseicin A1 (casA1) and caseicin A2 (casA2) were heterologously expressed in Escherichia coli BL21 (DE3) using the nisin leader peptide cloned in-frame to the C-terminal of the green fluorescent gene (mgfp5). Nisin protease (NisP) was used to cleave caseicin A1 (casA1) and caseicin A2 (casA2) from GFP-Nisin leader fusion proteins. Both heterologously expressed peptides (casA1 and casA2) inhibited the growth of L. monocytogenes, suggesting that casA1 and casA2 are either silent in the wild-type strains or are not secreted in an active form. The minimum inhibitory concentration (MIC) of casA1 and casA2, determined using HPLC-purified peptides, ranged from < 0.2µg/mL to 12.5µg/mL when tested against Listeria ivanovii, Listeria monocytogenes, and Listeria innocua, respectively. A higher MIC value (25µg/mL) was recorded for casA1 and casA2 when Enterococcus faecium HKLHS was used as the target. The molecular weight of heterologously expressed casA1 and casA2 is 5.1 and 5.2kDa, respectively, as determined with tricine-SDS-PAGE. Further research is required to determine if genes within Cas1 and Cas2 render immunity to other class IIa bacteriocins.

INHIBITION OF METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) BIOFILM: THE ESSENTIAL ROLE AND POTENTIAL USAGE OF BACTERIOCINS

Background: The potential of Methicillin-Resistant Staphylococcus aureus (MRSA) to develop biofilms and its resistance to antibiotics become major worldwide issue. Complementary anti-microbial strategies have been used recently, in particular for the treatment of MRSA biofilm-associated resistance. Purpose: To review the potential, essential role, and mechanism of bacteriocin that can inhibit MRSA biofilms. The review was conducted by searching and analyzing published articles from Elsevier, ProQuest and PubMed database. Review: Globally, the incidence of MRSA in 85 countries based on WHO surveillance reaches more than 20%. Biofilm, as one of the virulence factors of MRSA, can result in the failure of antibiotic therapy. According to reports, bacteriocins, such as peptides synthesized by Gram-negative and Gram-positive bacteria, have antimicrobial activity that has the potential to inhibit antibiotic-resistant pathogens and biofilms formed by MRSA. Result: The bacteriostatic and bactericidal activity of bacteriocins against MRSA has been shown through research across several countries on the usage of bacteriocins, which was isolated from different types of bacteria against MRSA biofilms. Bacteriocins contribute to the inhibition of MRSA biofilms by inhibiting the synthesis of cell walls, leading to pores in the cytoplasmic membranes of bacterial cells, interrupting the synthesis of extracellular membranes, disrupting cell membranes, and reducing the number of planktonic cells within MRSA biofilms. Conclusion: Bacteriocins have an effective mechanism for treating MRSA biofilms with low toxicity and risk of resistance, hence they are safe to be developed as complementary components to antibiotics in an effort to treat MRSA biofilms.

Impact of Temperature Variations on Bacteriocin Activity Against Spoilage Bacteria in Melon and Its Fermented Product 'Ogiri'

Impact of Temperature Variations on Bacteriocin Activity Against Spoilage Bacteria in Melon and Its Fermented Product 'Ogiri'

THE SYNERGISTIC EFFECTS OF LIPOPEPTIDES AND BACTERIOCINS PRODUCED BY Lactobacillus sp. OF HUMAN SAMPLES AGAINST CLINICAL PATHOGENS OF WOUND INFECTION

This study was performed for production, purification, characterization and evaluation the antibacterial activity of biosurfactant BS which were produced from local isolate Lactobacillus plantarum Z9 with bacteriocin and studying the synergistic effect .A total 100 different samples 85(%) isolates of Lactobacillus sp. were isolated from different sources and identified by biochemical tests then subjected to the primary and secondary screening processes to select the active isolate for bacteriocin and biosurfactant production. Among the vagina isolates screened, the results found that Lactobacillus sp. Z9 isolated from the clinical samples of Iraqi healthy women had the highest productivity of the bacteriocin and biosurfactant. Partial purification of biosurfactant that produced from L. plantarum Z9 was conducted using solvent system (chloroform: methanol, 2:1). A 1:1 ratio of n-butanol was used to extract of partially purified bacteriocin, where the bacteriocin activity up to 320 AU/ml against both Staphylococcus aureus and Pseudomonas aeruginosa respectively compared to 20 AU/ml before purification.. Antibacterial activity of Bacteriocin displayed a significant activity with inhibition zones diameter ranged from (11 to 26 mm) and (10 to 25 mm) against P. aeruginosa and S. aureus at concentration ranged from 50 to 200 mg/ml. Maximum antibacterial activity of bacteriocin against P. aeruginosa and S. aureus showed at concentration 200 mg/ml of bacteriocin. Partial purified lipopeptide of L. plantarum Z9 was examined against pathogenic bacteria using well diffusion method. The lipopeptide had inhibition zones diameter ranged from (14 to 28 mm) and (13 to 29 mm) against P. aeruginosa and S. aureus respectively at concentration ranged from 25 to 200 mg/ml. The combination of lipopeptide with bacteriocin increased the range of inhibition zones and made the pathogens sensitive.

The Antilisterial Effect of Latilactobacillus sakei CTC494 in Relation to Dry Fermented Sausage Ingredients and Temperature in Meat Simulation Media

Listeria monocytogenes, the causative agent of listeriosis, is a relevant pathogen in dry fermented sausages (DFSs), and the application of antilisterial starter cultures is an effective intervention strategy to control the pathogen during DFS production. The effect of factors in relation to DFS formulation and production, NaCl (0–40 g/L), Mn (0.08–0.32 g/L), glucose (0–40 g/L) and temperature (3–37 °C), on the behaviour of L. monocytogenes when cocultured with Latilactobacillus sakei 23K (non-bacteriocinogenic) and CTC494 (bacteriocinogenic) strains was studied through a central composite design in meat simulation media. L. sakei and L. monocytogenes counts, pH, lactic acid production and bacteriocin activity were determined in mono and coculture. The pH decrease and lactic acid production were highly influenced by glucose, while production of sakacin K by L. sakei CTC494 was observed at moderate (10 and 20 °C), but not at the lowest (3 °C) and highest (37 °C), temperatures. Coculture growth had no effect on the acidification and bacteriocin production but inhibited and inactivated L. monocytogenes when L. sakei 23K entered the early stationary phase and when L. sakei CTC494 produced sakacin K. Optimal conditions for achieving a 5-log units reduction of L. monocytogenes were at 20 °C, 20 g/L of NaCl, 0.20 g/L of Mn and 40 g/L of glucose, those highlighting the importance of considering product formulation and fermentation conditions for bioprotective starter cultures application.

Limosilactobacillus fermentum strains MC1 and D12: Functional properties and exopolysaccharides characterization

Lactic acid bacteria (LAB) produce a broad spectrum of exopolysaccharides (EPSs), commonly used as texturizers in food products. Due to their potential contribution to LAB probiotic properties, like adhesion to human epithelial cells and competitive exclusion of pathogens from human intestinal epithelial cells, this study was focussed on the structural and functional characterization of the EPSs produced by two Limosilactobacillus fermentum strains – MC1, originating from mother's milk, and D12, autochthonous from Croatian smoked fresh cheese. Whole-genome sequencing and functional annotation of both L. fermentum strains by RAST server revealed the genes involved in EPS production and transport, with some differences in functionally related genes. EPSs were extracted from the cell surface of both bacterial strains and purified by size-exclusion chromatography. Structural characterization of the EPSs, achieved by chemical analyses and 1D and 2D NMR spectroscopy, showed that both strains produce an identical mixture of three different EPSs containing galactofuranose and glucopyranose residues. However, a comparison of the functional properties showed that the MC1 strain adhered better to the Caco-2 cell line and exhibited stronger antimicrobial effect against Salmonella enterica serovar Typhimurium FP1 than the D12 strain, which may be attributed to the potential bacteriocin activity of the MC1 strain.

Assessment of bacteriocin production by clinical Pseudomonas aeruginosa isolates and their potential as therapeutic agents

IntroductionBacterial infections and the rising antimicrobial resistance pose a significant threat to public health. Pseudomonas aeruginosa produces bacteriocins like pyocins, especially S-type pyocins, which are promising for biological applications. This research focuses on clinical P. aeruginosa isolates to assess their bacteriocin production, inhibitory spectrum, chemical structure, antibacterial agents, and preservative potential.MethodsThe identification of P. aeruginosa was conducted through both phenotypic and molecular approaches. The inhibitory spectrum and antibacterial potential of the isolates were assessed. The kinetics of antibacterial peptide production were investigated, and the activity of bacteriocin was quantified in arbitrary units (AU ml−1). Physico-chemical characterization of the antibacterial peptides was performed. Molecular weight estimation was carried out using SDS–PAGE. qRT-PCR analysis was employed to validate the expression of the selected candidate gene.ResultThe antibacterial activity of P. aeruginosa was attributed to the secretion of bacteriocin compounds, which belong to the S-type pyocin family. The use of mitomycin C led to a significant 65.74% increase in pyocin production by these isolates. These S-type pyocins exhibited the ability to inhibit the growth of both Gram-negative (P. mirabilis and P. vulgaris) and Gram-positive (S. aureus, S. epidermidis, E. hirae, S. pyogenes, and S. mutans) bacteria. The molecular weight of S-type pyocin was 66 kDa, and its gene expression was confirmed through qRT-PCR.ConclusionThese findings suggest that S-type pyocin hold significant potential as therapeutic agents against pathogenic strains. The Physico-chemical resistance of S-type pyocin underscores its potential for broad applications in the pharmaceutical, hygiene, and food industries.

Influence of different culture media on the antimicrobial activity of Pediococcus pentosaceus ST65ACC against Listeria monocytogenes.

Pediococcus pentosaceus ST65ACC is a bacteriocinogenic lactic acid bacteria (LAB) isolated from Brazilian artisanal cheese that is capable of inhibiting different food pathogens, mainly Listeria monocytogenes. The production of bacteriocins can be influenced by several growth conditions, such as temperature, pH, and medium composition. This study aimed to evaluate the effect of different culture media on the production of bacteriocins and antimicrobial activity of P. pentosaceus ST65ACC on L. monocytogenes Scott A. The strains were inoculated alone and in coculture in four different media: BHI broth, MRS broth, meat broth, and reconstituted skim milk (RSM) 10% (w/v). The culture media were then incubated at 37°C for 96h, and count analysis, pH measurement, and bacteriocin production were performed at 0, 24, 48, 72 and 96h. L. monocytogenes was inhibited to nondetectable levels in coculture with P. pentosaceus ST65ACC in MRS broth within 96h, consistent with the high production of bacteriocin throughout the analysis period (3,200-12,800 AU/mL). However, lower inhibitory activities of P. pentosaceus ST65ACC on L. monocytogenes Scott A were recorded in BHI, RSM, and meat broth, with low or no production of bacteriocins at the analyzed times. The composition of these culture media may have repressed the production and activity of bacteriocins and, consequently, the antagonist activity of P. pentosaceus ST65ACC on L. monocytogenes Scott A. The results showed that the antimicrobial activity was more effective in MRS broth, presenting greater production of bacteriocins and less variability when compared to the other media analyzed.

Anti-Listerial Activity of Bacteriocin-like Inhibitory Substance Produced by Enterococcus lactis LBM BT2 Using Alternative Medium with Sugarcane Molasses.

Listeria monocytogenes is a foodborne pathogen that contaminates food-processing environments and persists within biofilms on equipment, thus reaching final products by cross-contamination. With the growing demand for clean-label products, the search for natural antimicrobials as biopreservants, such as bacteriocins, has shown promising potential. In this context, this study aimed to evaluate the anti-listerial action of bacteriocins produced by Enterococcus lactis LBM BT2 in an alternative medium containing sugarcane molasses (SCM). Molecular analyses were carried out to characterize the strain, including the presence of bacteriocin-related genes. In the kinetic study on SCM medium E. lactis, LBM BT2 showed biomass and bacteriocin productions similar to those observed on a sucrose-based medium (control), highlighting the potential of the sugarcane molasses as a low-cost substrate. Stability tests revealed that the molecule remained active in wide ranges of pH (4-10) and temperature (60-100 °C). Furthermore, the proteolytic treatment reduced the biomolecule's antimicrobial activity, highlighting its proteinaceous nature. After primary purification by salting out and tangential flow filtration, the bacteriocin-like inhibitory substance (BLIS) showed bacteriostatic activity on suspended L. monocytogenes cells and against biofilm formation at a concentration of 0.625 mg/mL. These results demonstrate the potential of the produced BLIS as a biopreservative in the food industry.

Phenotypic and Genotypic Criteria for the Screening of Highly Active S-Type Pyocins Pseudomonas aeruginosa Producers

Bacteriocins of Pseudomonas aeruginosa, especially S-type pyocins, show high efficiency as analogs of antimicrobial drugs. Various screening methods can be used to identify producers of highly active pyocins, but there are no clear criteria for selecting perspective strains. The aim of this work was to determine criteria that can be used during phenotypic and genotypic screening for the selection of perspective highly active S-type pyocin P. aeruginosa producers. Methods. The objects of investigation were 40 P. aeruginosa strains. Pyocins were obtained from each culture, relative coefficients of activity spectrum and sensitivity were determined for all the strains used. The obtained results of the phenotypic screening were compared with the data of the genotypic screening. Results. The use of the proposed method of activity assessment according to the lysis intensity made it possible to phenotypically assess the expression of pyocin genes. It was established that according to the new criteria, only one strain — P. aeruginosa UCM B-333 — can be included in the group of the most active pyocin producers that inhibit the growth of more than 75% of indicator cultures. The majority of representatives of maximally and highly active producers were characterized by high resistance to the action of other pyocins, which can be considered as an additional criterion for the selection of perspective strains. During genotypic screening, it was established that the quantity of pyocin genes in the genome cannot be interpreted as a clear criterion of the producer’s perspective. However, 50% of representatives of maximally and highly active pyocin producers were characterized by the presence of two pyocin genes, while in 47.7% of moderately active and 54.5% of low active producers, one pyocin gene was detected more often. It was established that with widening the bacteriocin activity spectrum, the detection frequency of pyocin S1 and S5 genes increases, and for pyocin S2 and S3 genes — decreases. Thus, among the producers of maximally and highly active bacteriocins, pyocin S1 and S5 genes were identified with the highest frequency — 42.8% and 78.6%, and pyocin S2 and S3 genes — with the lowest one — 28.6% and 7.1%, respectively. Gene of pyocin S4 with tRNase activity were detected with equally high frequency in all groups of producers. Conclusions. The method of activity assessment by the lysis intensity allows not only to determine the presence of pyocins, but also to phenotypically evaluate the level of their expression, which is an important criterion for the selection of perspective producers. Bacteriocins with a wider activity spectrum are synthesized by P. aeruginosa strains with higher resistance to the action of pyocins from other cultures. The most optimal genotypic criterion for the selection of a highly perspective pyocin producer, detection of genes combination of bacteriocins with different mechanisms of action — with DNase activity (pyocin S1) and the ability to pore formation (pyocin S5) — can be considered.

Gut Distribution, Impact Factor, and Action Mechanism of Bacteriocin-Producing Beneficial Microbes as Promising Antimicrobial Agents in Gastrointestinal Infection.

Gastrointestinal (GI) infection by intestinal pathogens poses great threats to human health, and the therapeutic use of antibiotics has reached a bottleneck due to drug resistance. The developments of antimicrobial peptides produced by beneficial bacteria have drawn attention by virtue of effective, safe, and not prone to developing resistance. Though bacteriocin as antimicrobial agent in gut infection has been intensively investigated and reviewed, reviews on that of bacteriocin-producing beneficial microbes are very rare. It is important to explicitly state the prospect of bacteriocin-producing microbes in prevention of gastrointestinal infection towards their application in host. This review discusses the potential of gut as an appropriate resource for mining targeted bacteriocin-producing microbes. Then, host-related factors affecting the bacteriocin production and activity of bacteriocin-producing microbes in the gut are summarized. Accordingly, the multiple mechanisms (direct inhibition and indirect inhibition) behind the preventive effects of bacteriocin-producing microbes on gut infection are discussed. Finally, we propose several targeted strategies for the manipulation of bacteriocin-producing beneficial microbes to improve their performance in antimicrobial outcomes. We anticipate an upcoming emergence of developments and applications of bacteriocin-producing beneficial microbes as antimicrobial agent in gut infection induced by pathogenic bacteria.

Studies on the mechanisms of action and development of resistance to class II bacteriocins of Gram-positive bacteria

Bacteriocins are peptides or proteins produced by bacteria to kill or inhibit the growth of other bacteria inhabiting the same ecological niche. The growing interest in bacteriocins reflects their potential use in food preservation and treatment of infections caused by antibiotic-resistant pathogenic bacteria, among other applications. The number of published studies on the identification of new bacteriocin-producing strains is constantly increasing. At the same time, there is a noticeable lack of research describing the mechanisms of action of most newly identified bacteriocins, as well as the mechanisms leading to the development of resistance to these bacteriocins and cross-resistance to antibiotics. Detailed understanding of these issues will allow to develop guidelines ensuring the most effective, safe and long-term use of bacteriocins without the risk of resistance development. This work describes the main assumptions of the doctoral dissertation of Aleksandra Tymoszewska, which objectives were to characterize the mechanisms of action and of resistance to class II bacteriocins of Gram-positive bacteria. Using the model bacterium Lactococcus lactis, two groups of bacteriocins were examined: (i) garvicins Q, A, B and C, and BacSJ; and (ii) aureocin A53 (AurA53)- and enterocin L50 (EntL50)-like bacteriocins. Bacteriocins of group (i) have been shown to recognize susceptible cells and form pores in the cell membrane using a specific receptor, the mannose-specific phosphotransferase system (Man-PTS), and sensitive bacteria have been shown to acquire resistance to the these bacteriocins by modifying the structure of Man-PTS. On the other hand, the acquisition of resistance to group (ii) membrane-targeting and receptor-independent bacteriocins occurs through changes in the structure of the bacterial cell wall and membrane, which are induced by changes in the expression of proteins involved in lipid metabolism or components of the YsaCB-KinG-LlrG regulatory system. The results shed new light on previous views on the mechanisms of action of bacteriocins and open up opportunities for their further study.

Enhanced production of bacteriocin by Bacillus subtilis ZY05.

Bacteriocin-producing strains were isolated from the soil of the rice field, screened out using an agar-well diffusion assay against six indicator bacterial strains, and the highest among them was selected for further investigation. The study focuses on how different growing conditions affect bacteriocin production. One-parameter-at-a-time (OPAT) and a central composite design of response surface methodology (RSM) were used to perform the optimization in two steps. In the OPAT trials, bacteriocin synthesis was elevated by 29%, 45%, and 34%, by employing sucrose as a carbon source and changing the NaCl concentration and pH at 7, respectively. To determine the linear, squared, and interaction correlations among the process variables to predict the ideal conditions for production, a four-factor central composite design (CCD) of RSM was used. It was determined that the analysis of variance (ANOVA), which produces a recognized model using RSM, is sufficient to describe bacteriocin production regarding activity (R2 = 0.9606). The ideal conditions for increased production were 1.51% sucrose concentration, 1.59% NaCl concentration, pH 6.35, and 28.66 (about 29) hours of incubation. The value predicted by RSM (4051.55 AU/mL) was approximately two times greater than the value of a non-optimized medium. The experimental value of 4403.85 AU/mL was closer to the expected value. According to the data, increasing bacteriocin activity required employing the ideal sucrose concentration, NaCl concentration, and incubation time. The partially purified bacteriocin was found stable at temperatures between 24 and 50°C and at pH 5-8. The molecular weight purified bacteriocin was determined to be between 13 and 35kDa.

Double emulsion (W/O/W) microcapsule preparation of novel bacteriocin lactococcin036019 with synergistic compound vitamin C prolongs the antibacterial activity in food matrix

Application of bacteriocins in food preservation encounters the issue of activity impairment. This study intends to find a comprehensive solution to the enhancement of bacteriocin activity. Firstly, several food matrices were found to significantly reduce the antibacterial activity of bacteriocin lactococcin036019. Subsequently, vitamin C and carvacrol were both found to display a synergistic effect with bacteriocin against Staphylococcus aureus. Thereafter, double emulsion containing lactococcin036019 and vitamin C was successfully prepared. Spray drying of double emulsion with lactococcin036019 and vitamin C resulted in microcapsule powder with the particle size and entrapment efficiency of 9.10 μm and 56.18%, respectively. This microcapsule powder reduced S. aureus number by around 5 lg cfu/mL at 24 h and displayed continuous antibacterial activity in soymilk. Besides, the microcapsule powder with bacteriocin and vitamin C showed remarkable stability during storage. The double emulsion microcapsules prepared in this study demonstrate great potential in long-term preservation of food.

The quorum sensing peptide BlpC regulates the transcription of genes outside its associated gene cluster and impacts the growth of Streptococcus thermophilus.

Bacteriocin production in Streptococcus thermophilus is regulated by cell density-dependent signaling molecules, including BlpC, which regulates transcription from within the bacteriocin-like peptide (blp) gene cluster. In some strains, such as S. thermophilus ST106, this signaling system does not function properly, and BlpC must be supplied exogenously to induce bacteriocin production. In other strains, such as S. thermophilus B59671, bacteriocin (thermophilin 110 in strain B59671) production occurs naturally. Here, transcriptomic analyses were used to compare global gene expression within ST106 in the presence or absence of synthetic BlpC and within B59671 to determine if BlpC regulates the expression of genes outside the blp cluster. Real-time semi-quantitative PCR was used to find genes differentially expressed in the absence of chromosomal blpC in the B59671 background. Growth curve experiments and bacteriocin activity assays were performed with knockout mutants and BlpC supplementation to identify effects on growth and bacteriocin production. In addition to the genes involved in bacteriocin production, BlpC affected the expression of several transcription regulators outside the blp gene cluster, including a putative YtrA-subfamily transcriptional repressor. In strain B59671, BlpC not only regulated the expression of thermophilin 110 but also suppressed the production of another bacteriocin, thermophilin 13, and induced the same YtrA-subfamily transcriptional repressor identified in ST106. Additionally, it was shown that the broad-spectrum antimicrobial activity associated with strain B59671 was due to the production of thermophilin 110, while thermophilin 13 appears to be a redundant system for suppressing intraspecies growth. BlpC production or induction negatively affected the growth of strains B59671 and ST106, revealing selective pressure to not produce bacteriocins that may explain bacteriocin production phenotype differences between S. thermophilus strains. This study identifies additional genes regulated by BlpC and assists in defining conditions to optimize the production of bacteriocins for applications in agriculture or human and animal health.

Bacteriocin Activity of Yogurt Probiotics on Increasing Production of Laying Hens

Bacteriocin Activity of Yogurt Probiotics on Increasing Production of Laying Hens