School of Pure and Applied Sciences

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End date: 2025Subject: search.filters.subject.Bacteriocin

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    Antimicrobial Activity and Characteristics of Bacteriocin Producing Bacillus subtilis against Mastitis Pathogens
    (American Journal of Food Science and Technology, 2021-04-20) Wafula, Eliud N.; et.al
    The use of drugs and antibiotics has increased the resistance of pathogenic bacteria in both animals and humans. This has been a significant problem and therefore triggers the investigation of novel antimicrobial agents produced by a bacterial strain of low virulence and having antimicrobial activity with a wide range of clinical significance. The use of bacteriocin has been extensively used in food industries, animals, and pharmaceutical industries. This is because it has been linked to antimicrobial activity, which has specific self-protection mechanisms. This study sought to evaluate antimicrobial activity and characteristics of bacteriocin producing Bacillus subtilis against Mastitis pathogens. For the screening of the isolates for bacteriocin properties against mastitis pathogens, antimicrobial activity was done using well diffusion methods on the nutrient agar. The results were obtained after 24hours and 48hours. Physiochemical characterization of the bacteriocin from Bacillus subtilis was determined at different temperatures of 60°C to 121°C for 15 minutes and monitor the effect of the temperature. The bacteriocin was also prepared at different pH (3-9) and incubated at room temperature; each sample's residual activity was determined against the indicator organisms. Metal ions (Cu2+, Zn2+, and Fe2+) on crude bacteriocin activity were determined to assess the residual antimicrobial activity by agar well diffusion assay. The results showed that bacteriocins from Bacillus subtilis were effective against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumonia. Physiochemical characterization showed that bacteriocin from different isolates had no inhibition from pH 3-5 and varied inhibition from pH 6-9 across the test organisms' isolates. On the temperature, crude bacteriocins at a temperature of 50°C to 60°C showed no activity loss based on initial activity. As temperature increases to 70°C to 80°C, there is reduced the bacteriocin activity of about 20%. 100°C had a 40% loss of the bacteriocin activity and 121°C with more than 50% loss of the activity. On metal ions, Cu2+, Fe2+, Zn2+ had a varied effect on bacteriocin activity against test organisms.
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    Isolation and Characterization of Bacteriocin-Producing Lactic Acid Bacteria from Mbithi: A Kenyan Traditional Fermented Porridge
    (Journal of Harbin Engineering University, 2025-02-23) Wafula, Eliud N.; et.al
    Introduction: Mbithi is a non-alcoholic, spontaneously fermented product that remains a traditional food cuisine in Kenya, valued for its nutritional properties. Lactic acid bacteria (LAB) are utilized in the food business as a starting culture, with their preservation properties linked to their ability to produce bacteriocins. Due to their eco-friendly properties, LAB's bacteriocins offer a viable solution to the health risks associated with chemical preservatives in the food industry. Objectives: This study presents results on isolating and characterizing bacteriocin-producing lactic acid bacteria from Mbithi. Methods: Lactic acid bacteria (LAB) were isolated using MRS and M17 agar. These isolates were then phenotypically characterized, including biochemical and physical tests. The isolates were screened for antimicrobial activity by agar well-diffusion assay, while genotypic characterization was performed based on the 16S rRNA gene sequence. Results: A total of 50 LAB strains were extracted. Of the fifty (50) isolates, 47 (94%) were selected due to their demonstration of gram-positive characteristics and catalase activity. Furthermore, 12 isolates were heterofermentative for they fermented glucose, whereas (35) isolates did not metabolize glucose (homofermentative). The results on salinity, acidity, and temperature demonstrated that most of the isolates tolerated the salinity with 6.5% of NaCl, acidic at pH 2.0 and pH 2.5 and temperature of 45°C. Nonetheless, none of the isolates withstood a temperature of 10℃. From the inhibition tests, we identified 10 candidate isolates, including three isolates—FP2 24, FP2 28, and FP22—that exhibited antagonism against all evaluated indicator pathogenic microorganisms. The three isolates exhibited inhibitory activity against E. coli, Bacillus subtilis, and Staphylococcus aureus, with inhibition zones of 21±1.41, 26±1.41, and 21±1.41, respectively, and a P-value of less than (P<0.05, P=0.000). The phylogenetic and Blast analyses indicated that the isolates were categorized into five clusters: Lactiplantibacillus, Levilactobacillus, Pediococcus, Weisella, and Leuconostoc, with the majority clustering within the Lactiplantibacillus genus, with similarities ranging from (95.1%-100%). Conclusions: The findings revealed potential isolates showing antagonistic activity against pathogenic indicators, suggesting their possible production of secondary metabolites. Despite this research presenting promising outcomes, further characterization is requested to get insights on probiotics properties for the usage of the isolates in preservatives in the food industry domains.