Antibacterial and Antioxidant Activity of Extracts from Selected Probiotic Bacteria

Probiotic extracts can potentially be used as bio-preservatives and in reduction of oxidative stress. The study investigated the antibacterial and antioxidant activity of methanol extracts from freeze-dried cells of probiotic Lactobacillus strains identified using molecular techniques. The quantitative microplate method, which employed p-iodonitrotetrazolium (INT) and the method by Brand-Williams et al. (1995) were employed to investigate quantitatively the antibacterial and the antioxidant activity, respectively, of probiotic extracts. The MIC values extracts from most probiotic strains, tested against indicator bacterial pathogens, were in the range of 1.25 – 5 mg/mL while that of Lb. casei strain B and Lc. lactis subsp lactis strain X was at least 20 mg/mL after 24 h of incubation at 37°C. At the highest extract concentration of 20 mg/mL used in the study, Lb. acidophilus, Lb. rhamnosus and Lb. casei strains had 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activities of 77.9 - 86.1%, 45.7 - 86.4% and 36.9 – 45.8% respectively. Quantitative antibacterial and antioxidant activities of methanol extracts from freeze-dried cells of probiotic Lactobacillus strains was determined for the first time.