Physical chemical and biological characterization of a new bacteriocin produced by Bacillus cereus NS02

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.

Characterization of the Novel Leaderless Bacteriocin, Bawcin, from Bacillus wiedmannii

The rise of drug-resistant bacteria is a major threat to public health, highlighting the urgent need for new antimicrobial compounds and treatments. Bacteriocins, which are ribosomally synthesized antimicrobial peptides produced by bacteria, hold promise as alternatives to conventional antibiotics. In this study, we identified and characterized a novel leaderless bacteriocin, bawcin, the first bacteriocin to be characterized from a Bacillus wiedmannii species. Chemically synthesized and purified bawcin was shown to be active against a broad range of Gram-positive bacteria, including foodborne pathogens Staphylococcus aureus, Bacillus cereus, and Listeria monocytogenes. Stability screening revealed that bawcin is stable over a wide range of pH (2.0-10.0), temperature conditions (25-100 °C), and against the proteases, papain and pepsin. Lastly, three-dimensional structure homology modeling suggests that bawcin contains a saposin-fold with amphipathic helices and a highly cationic surface that may be critical for membrane interaction and the subsequent cell death of its targets. This study provides the foundational understanding of the activity and properties of bawcin, offering valuable insights into its applications across different antimicrobial uses, including as a natural preservative in food and livestock industries.

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.

Characterization of the antimicrobial activity produced by Bacillus sp. isolated from wetland sediment

Bacteria of the genus Bacillus sp. present the potential for inhibiting various pathogens, making them a promising starting point in the search for new antimicrobial substances. In this study, bacteria were isolated from sediment samples from humid areas of a Natural Conservation Unit in the state of Rio Grande do Sul, Brazil. The isolate Bacillus sp. sed 1.4 was selected for production of antimicrobial activity, and was characterized by MALDI-TOF and 16S rDNA sequencing. Phylogenetic analysis showed that Bacillus sed 1.4 was closely related to Bacillus altitudinis and Bacillus pumilus. The cell-free supernatant was partially purified using ammonium sulfate precipitation, gel filtration chromatography (Sephadex G-200) and an ultrafiltration membrane. Partial purification resulted in specific activity of 769.23 AU/mg, with a molecular mass of approximately 148 kDa. This antimicrobial substance showed stability at 100°C for 5 min, and was inactivated by proteolytic enzymes. An antimicrobial effect against Listeria species was observed. Considering the importance of the Listeria genus in the area of food safety, this antimicrobial activity should be further explored, specifically in the field of dairy products and with a focus on food biopreservation studies.

Bacillus sp. Bacteriocins: Natural Weapons against Bacterial Enemies

BACKGROUND

Currently, antibiotic-resistant pathogenic bacteria are emerging as an important health problem worldwide. The search for new compounds with antibiotic characteristics is the most promising alternative. Bacteriocins are natural compounds that are inhibitory against pathogens, and Bacillus species are the major producers of these compounds, which have shown antimicrobial activity against clinically important bacteria. These peptides not only have potential in the pharmaceutical industry but also in food and agricultural sectors.

OBJECTIVE

We provide an overview of the recent bacteriocins isolated from different species of Bacillus including their applications and the older bacteriocins.

RESULTS

In this review, we have revised some works about the improvements carried out in the production of bacteriocins.

CONCLUSION

These applications make bacteriocins very promising compounds that need to study for industrial production.

Synergistically-acting Enterocin LD3 and Plantaricin LD4 Against Gram-Positive and Gram-Negative Pathogenic Bacteria

The efficacy of antimicrobials is an important aspect during their applications in food and therapeutics. In this study, combination of two bacteriocins, enterocin LD3 and plantaricin LD4, was studied against two pathogenic bacteria, Staphylococcus aureus subsp. aureus ATCC25923 and Salmonella enterica subsp. enterica serovar Typhimurium ATCC13311 for increasing their potency and bactericidal activity. The minimal inhibitory concentrations (MICs) of enterocin LD3 and plantaricin LD4 against Staph. aureus subsp. aureus ATCC25923 were 180 and 220 μg/mL, whereas in combination, reduced to 115 μg/mL, respectively. The MICs of enterocin LD3 and plantaricin LD4 against Salm. enterica subsp. enterica serovar Typhimurium ATCC13311 were 240 and 320 μg/mL, respectively, whereas in combination, these were found to be 130 μg/mL, respectively. The fractional inhibitory concentration (FIC) indices calculated as 0.50 against Staph. aureus subsp. aureus ATCC25923 and 0.43 against Salm. enterica subsp. enterica serovar Typhimurium ATCC13311 were found to be ≤ 0.5 indicating the synergy. The isobologram showed MIC of combined bacteriocins falls below the plotted straight line further signifies synergy. The growth response of Staph. aureus subsp. aureus ATCC25923 and Salm. enterica subsp. enterica serovar Typhimurium ATCC13311 was significantly reduced in the presence of combined bacteriocins in comparison with their individual effects. The number of dead cells was higher as a result of combined effect as compared with their independent effect evidenced by fluorescent microscopy. Transmission electron microscopy (TEM) revealed the higher disruption of cell membrane in the combined bacteriocin-treated cells as compared with alone effects. The FTIR spectra of enterocin LD3-treated cells showed alteration at ~ 1,451.82 and ~ 1,094.30/cm corresponding to nucleic acids and phospholipids suggesting its interaction with cell membrane and nucleic acids. In contrast, plantaricin LD4-treated cells did not show such alterations suggesting plantaricin LD4 may kill target cells using other mechanism. Our data suggest that different mode of action of both bacteriocins results in division of labour and may be responsible for their synergistic activity against target cells. Similarly, the synergistic effect of bacteriocins was also observed against other pathogenic bacteria such as Proteus mirabilis ATCC43071, Pseudomonas aeruginosa ATCC27853 and Escherichia coli ATCC25922. These bacteriocins, therefore, act synergistically against target pathogens and may be applied in appropriate combinations for food safety and medical applications.

Biomanufacturing process for the production of bacteriocins from Bacillaceae family

Members of Bacillaceae family are of major interest in medical industry due to vast antimicrobial peptides they produce as therapeutic agents. For decades, synthetic and natural occurring antibiotics have been used to treat infectious diseases, but heavy dependence on these drugs has led to significant drawbacks which propel continuous development of new antibiotics generation. Recent findings have shown several bacteriocins of Bacillaceae as promising alternatives to the conventional drugs to combat the emergence of new drug-resistant pathogens. In this present review, Bacillaceae bacteriocins’ classification such as lantibiotics and thiazole/oxazole-modified microcins as well as their biochemical characterization such as sensitivity to enzymes, temperature, pH and chemicals are described. This article enlightens on the medical application of several Bacillaceae bacteriocins emphasizing those that underwent and on-going preclinical trials. This review also discusses the development of Bacillaceae bacteriocins production, focusing strains selection and fermentation factors such as inocula size, medium (carbon, nitrogen, minerals sources), temperature, pH, agitation and aeration rate, dissolved oxygen tension (DOT), fermentation time, inducers and mode of operation via various statistical methods for their optimization. It also highlights recent advance in the production of bioengineered and recombinant bacteriocins in bioreactors system which are rarely disclosed in literature.

Effect of Bacillus cereus peptide conjugated with nanoporous silica on inactivation of Listeria monocytogenes in apple juice, as an ecofriendly preservative

Bacteriocins are ribosomally synthesized antimicrobial proteins/peptides. They are of great interest in the food processing industries as potential natural preservative agent to control food-borne pathogens. Bacillus spp. are one among the potential probiotics receiving more attention since they produce a broad spectrum of antimicrobial bioactive peptides. In this study, a small-scale medium composition and bioprocessing parameters were statistically optimized to increase the yield of bacteriocin namely cerein from Bacillus cereus NS02 showing antagonism against a wide range of food-borne pathogens. The cerein was partially purified, characterized, and evaluated for their optimal reaction condition. It was subjected to surface adsorption onto food-grade silica to evaluate its maximal adsorption, reached at 4 h, 40 °C, pH 6-7, and at the initial concentration of 200 AU mL^-1. The effectiveness of silica-adsorbed and silica-free cerein was checked in Listeria monocytogenes inoculated fresh apple juice and demonstrated biopreservative activity. In juice treated with silica-cerein, the colony forming unit (CFU) was found to be less in count on the 15th day of storage at 4 °C whereas, free-cerein was found to contain 3.8 log CFU mL^-1. While, on the same day of storage, the control juice contained the strength of 14.6 log CFU mL^-1. Based on the above, this study concludes that the identified heat stable low molecular weight peptide cerein from B. cereus NS02 could serve as a potential biopreservative with effective antilisterial activity in the food system. However, a more detailed study is required to determine if their quality change especially the effect of cerein in organoleptic and nutritional properties of food beyond their addition is necessary, before it is to be exploited as an ecofriendly biopreservative.

Kinetic modeling of bacteriocin-like inhibitory substance secretion by Pediococcus acidilactici Kp10 and its stability in food manufacturing conditions

This paper deliberates the modelling and validation of bacteriocin-like inhibitory substance (BLIS) secretion by Pediococcus acidilactici Kp10 at different agitation speeds in a stirred tank bioreactor. A range of models namely the re-parameterised logistic, Luedeking-Piret and maintenance energy were assessed to predict the culture performance of the said bacterium. Growth of P. acidilactici Kp10 was enhanced with increased agitation speed up to 600 rpm while BLIS secretion was maximum at 400 rpm but decreased at higher agitation speed. Growth of P. acidilactici aptly subscribed to the re-parameterised logistic model while BLIS secretion and lactose consumption fitted well with the Luedeking-Piret model. The models revealed a relationship between growth of the bacterium and BLIS secretion. Bacterial growth and BLIS secretion were largely affected by the agitation speed of the stirred tank bioreactor which regulated the oxygen transfer to the culture. BLIS secretion by P. acidilactici Kp10 was however enhanced in oxygen-limited culture. The study also assessed BLIS from the perspective of its stability when subjected to factors such as temperature, pH and detergents. Results showed that BLIS produced by this strain was not affected by heat (at 25-100 °C for 20 min and at 121 °C for 15 min), surfactant (Tween 40, 60 and 80 and urea), detergents (up to 1% SDS), organic solvents (50% each of acetone, methanol and ethanol) and stable in a wide range of pH (2-10). The above information are pertinent with reference to commercial applications of this bacterial product in food manufacturing which invariably involve various sterilization processes and subjected to a wide pH range.

The biodiversity of Lactobacillus spp. from Iranian raw milk Motal cheese and antibacterial evaluation based on bacteriocin-encoding genes

Lactobacilli, as the largest group of lactic acid bacteria, produce large amounts of antimicrobial metabolites such as organic acids, fatty acids, ammonia, hydrogen peroxide, diacetyl and bacteriocin, which inhibit the growth of pathogenic bacteria and increase shelf life of food. The aim of this study was to identify the Lactobacillus spp. isolated from Iranian raw milk Motal cheese and to detect the presence of bacteriocin genes in the isolated Lactobacillus strains exhibiting antimicrobial activity. For this purpose, 6 Motal cheese samples from Dasht-e-Moghan region, Iran, were subjected to microbial characterization. Nineteen Lactobacillus spp. were isolated and subsequently identified based on biochemical and molecular methods. According to the sequencing of isolates, Lactobacillus spp. consisted primarily of Lactobacillus brevis, Lactobacillus plantarum, Lactobacillus casei and Lactobacillus buchneri. The identified isolates were then evaluated for antimicrobial activity against Escherichia coli ATCC 25922, Listeria innocua ATCC 33090 and Staphylococcus aureus ATCC 25923. The results of PCR analysis using specific primers of genes encoding Bacteriocin, revealed the presence of Plantaricin A and Plantaricin EF in all Lactobacillus plantarum isolates and Brevicin 174A in 5 of Lactobacillus brevis isolates, whereas the gene encoding Pediocin PA-1 was not observed in any of examined isolates. It is therefore concluded that bacteriocinogenic isolates could be recommended as suitable candidates to be used as starter, adjunct-starter or antimicrobial agents for production of fermented and non-fermented products.

Design and recombination expression of a novel plectasin-derived peptide MP1106 and its properties against Staphylococcus aureus

A novel antimicrobial peptide MP1106 was designed based on the parental peptide plectasin with four mutational sites and a high level of expression in Pichia pastoris X-33 via the pPICZαA plasmid was achieved. The concentration of total secreted protein in the fermented supernatant was 2.134 g/l (29 °C), and the concentration of recombinant MP1106 (rMP1106) reached 1,808 mg/l after a 120-h induction in a 5-l fermentor. The rMP1106 was purified using a cation-exchange column, and the yield was 831 mg/l with 94.68 % purity. The sample exhibited a narrow spectrum against some Gram-positive bacteria and strong antimicrobial activity against Staphylococcus aureus at low minimal inhibitory concentrations (MICs) of 0.014, 1.8, 0.45, and 0.91 μM to S. aureus strains ATCC 25923, 29213, 6538, and 43300, respectively. Meanwhile, rMP1106 showed potent activity (0.03-1.8 μM) against 20 clinical isolates of methicillin-resistant S. aureus (MRSA). In addition, rMP1106 exhibited a broad range of thermostability from 20 to 100 °C. The higher antimicrobial activity of rMP1106 was maintained in neutral and alkaline environments (pH 6, 8, and 10), and its activity was slightly reduced in acidic environments (pH 2 and 4). The rMP1106 was resistant to the digestion of pepsin, snailase, and proteinase K and was sensitive to trypsin. It exhibited hemolytic activity of only 1.16 % at a concentration of 512 μg/ml and remained stable in human serum at 37 °C for 24 h. Furthermore, the activity of rMP1106 was minorly affected by 10 mM dithiothreitol and 20 % dimethylsulfoxide. Our results indicate that MP1106 can be produced on a large scale and has potential as a therapeutic drug against S. aureus.