Effects of carbon and nitrogen sources on bacteriocin-inhibitory activity of postbiotic metabolites produced by Lactobacillus plantarum I-UL4

Abstract

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 I-UL4.

Comparative Studies of Inhibitory and Antioxidant Activities, and Organic Acids Compositions of Postbiotics Produced by Probiotic Lactiplantibacillus plantarum Strains Isolated From Malaysian Foods

“…Thus, when incorporated in the formulated media, it had further promoted good bacterial cell growth and bacteriocin production as reported by Ooi et al (31) and Abbasiliasi et al (47). On top of that, the ingredients in MRS such as meat extract and peptone not only inhibit the growth but also reduce the antimicrobial activity of the bacteria (31,48). For the carbon source, glucose has been proven to be the best ingredient for bacteriocin production due to its simple structure as compared to other carbon sources such as sucrose (31,49).…”

“…Bacteria require sufficient carbon, nitrogen, and other nutrients in the growth medium to improve growth, metabolic activity, and production of vital metabolites (33). As reported previously, the optimization of fermentation media enhanced the bacteriocin inhibitory of postbiotic produced by L. plantarum I-UL4 (31). Moreover, L. plantarum postbiotics exerted higher inhibitory activity against various pathogenic bacteria such as E. coli, Salmonella enterica, Listeria monocytogenes, and VRE when inulin is included in the fermentation media (22).…”

“…The higher inhibitory activity exerted by postbiotics produced by using formulated media could be attributed to the higher concentration of yeast extract that contains amino acids and growth factors (47). Thus, when incorporated in the formulated media, it had further promoted good bacterial cell growth and bacteriocin production as reported by Ooi et al (31) and Abbasiliasi et al (47). On top of that, the ingredients in MRS such as meat extract and peptone not only inhibit the growth but also reduce the antimicrobial activity of the bacteria (31,48).…”

“…On top of that, the ingredients in MRS such as meat extract and peptone not only inhibit the growth but also reduce the antimicrobial activity of the bacteria (31,48). For the carbon source, glucose has been proven to be the best ingredient for bacteriocin production due to its simple structure as compared to other carbon sources such as sucrose (31,49). Furthermore, the inhibitory activity of postbiotics was influenced by bacteriocin production and organic acid production.…”

“…Furthermore, supplementation of L. plantarum postbiotics in feed improves the growth performance of livestock (23,24), laying performance (25), villus height (25,26), antioxidant activity in the blood (27), and immune response (24), and reduces adverse impacts on the physiological activities of broilers due to heat stress (28). However, the production of postbiotic metabolites is affected by various factors such as temperature and pH (29), strains of producer bacteria, and nutrient components of the growth medium (30,31).…”