Aims: Lactobacillus sp. has capability of producing an array of bioactive metabolites that exhibit probiotic effects. Therefore, the objective of this study was to determine the cytotoxicity effect of proteinaceous postbiotic metabolites (PPM) produced by Lactobacillus plantarum I-UL4 cultivated in different media composition on MCF-7 breast cancer cell. Methodology and results: L. plantarum I-UL4 was cultivated in yeast extract and modified de Man, Rogosa and Sharpe broth containing Tween 80 (CRMRS+T80) or without Tween-80 (CRMRS-T80). Human breast adenocarcinoma cell (MCF-7) was employed as cancer cell in this study. Cytotoxicity and antiproliferative effects of PPM were determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl Tetrazolium Bromide assay and Trypan Blue Dye Exclusion assay, whereas Acridine Orange/Propidium Iodide staining was employed to determine the cytotoxicity mechanism. PPM produced in CRMRS+T80 exerted cytotoxicity in a time and dose dependent manner that was selective towards MCF-7 cancer cell. Profound cytotoxicity with the lowest IC50 concentration of 10.83 µg was detected at 72 h of incubation, whereas the most potent antiproliferative effect revealed by the lowest viable cell population was observed at 24 h of incubation. PPM cultivated in CRMRS+T80 induced 80.87% of apoptotic MCF-7 cells at 48 h of incubation. Conclusion, significance and impact of study: PPM of L. plantarum I-UL4 cultivated in different media composition induced different levels of MCF-7 cancer cell death. The percentage of apoptotic MCF-7 cells treated with PPM cultivated in CRMRS+T80 increased significantly (p < 0.05) from 24 to 48 h of incubation. The results obtained in this study have revealed the potential of PPM produced by L. plantarum I-UL4 as human health supplement and as anticancer preventive agent. Keywords: Lactobacillus plantarum I-UL4; cytotoxic effect; proteinaceous postbiotic metabolites; media composition; breast cancer
Lactobacillus ; Probiotics

Aims: Postbiotic metabolites are metabolic compounds produced by probiotic lactic acid bacteria. These compounds produced by Lactobacillus sp. have been shown to be effective substitutes for in-feed antibiotic in livestock due to their broad inhibitory activity. Therefore, the aim of this study was to determine the effects of various carbon and nitrogen sources on the bacteriocin-inhibitory activity of postbiotic metabolites produced by Lactobacillus plantarum I-UL4. Methodology and results: The effects of various combinations of carbon and nitrogen sources on the bacteriocininhibitory activity (expressed as modified bacteriocin activity, MAU/mL) of postbiotic metabolites produced by L. plantarum I-UL4 were determined in basal media without micronutrients. The combination of glucose (20 g/L) and yeast extract (22 g/L) gave the best bacteriocin-inhibitory activity as compared to other combinations. Maximum bacteriocininhibitory activity of 1440 MAU/mL was achieved when 36.20 g/L of yeast extract was added as the sole nitrogen source in modified de Man, Rogosa and Sharpe (MRS) medium. The glucose concentration was further optimised to enhance the bacteriocin-inhibitory activity of the postbiotic metabolites. Lower bacteriocin-inhibitory activity was observed at 5, 10, 15 and 40 g/L in comparison to 20 g/L of glucose. Conclusion, significance and impact of study: Maximum bacteriocin-inhibitory activity of postbiotic metabolites was achieved at 1440 MAU/mL when 20 g/L of glucose and 36.20 g/L of yeast extract were added as the sole carbon and nitrogen sources respectively in the modified MRS medium. Optimisation of other micronutrients present in MRS media is necessary to further enhance the bacteriocin-inhibitory activity of postbiotic metabolites produced by L. plantarum IUL4.
Lactobacillus