Antioxidative potential of folate producing probiotic Lactobacillus helveticus CD6

Abstract

Folate producing Lactobacillus sp. CD6 isolated from fermented milk showed 98% similarity with Lactobacillus helveticus based on 16S rRNA gene sequence analysis. It was found to produce a folic acid derivative 5-methyl tetrahydrofolate (5-MeTHF). The intracellular cell-free extract of strain demonstrated antioxidative activity with the inhibition rate of ascorbate autoxidation in the range of 27.5% ± 3.7%. It showed highest metal ion chelation ability for Fe(2+) (0.26 ± 0.06 ppm) as compared to Cu(2+). The DPPH (α,α-Diphenyl-β-Picrylhydrazyl) radical scavenging activity for intact cells were found to be 24.7% ± 10.9% proved its antioxidative potential. Furthermore, it demonstrated 14.89% inhibition of epinephrine autoxidation, 20.9 ± 1.8 μg cysteine equivalent reducing activity and 20.8% ± 0.9% hydroxyl radical scavenging effect. The strain was evaluated for probiotic properties as per WHO and FAO guidelines. It showed 90.61% survival at highly acidic condition (pH 2.0), 90.66% viability in presence of synthetic gastric juice and 68% survivability at 0.5% bile concentration for 24 h. It was susceptible to many antibiotics which reduces the prospect to offer resistance determinants to other organisms if administered in the form of probiotic preparations. It showed in vitro mucus binding and antimicrobial activity against enteric pathogens like Salmonella typhimurium (NCIM 2501), Streptococcus pyogenes (NCIM 2608), and Staphylococcus aureus (NCIM 5021) and moreover it showed non- hemolytic activity on sheep blood agar.

Keywords: 5-methyl tetrahydrofolate; Ascorbate autoxidation; Fermented milk; Lactobacillus helveticus; Probiotic.

Fig. 1

Effect of different metal ions on SOD induction. Data are mean ± SD. Error bars represent SD. ns no significance; **P < 0.01, ***P < 0.001; n = 3 per group

Fig. 2

Effect of different metal ions on survival of bacteria. Data are mean ± SD. Error bars represent SD. ns no significance; ***P < 0.001; n = 3 per group

Fig. 3

Native gel electrophoresis and SOD staining activity. Lanes a–b: stained for SOD activity (a intracellular cell free extract of isolate; b SOD from bovine erythrocytes) Lanes c–e: stained with coomassie brilliant blue for protein pattern (c SOD from bovine erythrocytes; d & e intracellular cell free extract of isolate)