Free radical formation by Lactobacillus acidophilus NCFM is enhanced by antioxidants and decreased by catalase

• Published in: Food research international Vol. 79; pp. 81 - 87
• Main Authors: Hougaard, Anni B., Pindstrup, Helene, Arneborg, Nils, Andersen, Mogens L., Skibsted, Leif H.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-01-2016
• Subjects: Catalase; Electron spin resonance; Free radicals; Lactobacillus acidophilus; Quercetin; Rutin; Free radicals; Catalase; Lactobacillus acidophilus; Rutin; Electron spin resonance; Quercetin
• ISSN: 0963-9969; 1873-7145
• DOI: 10.1016/j.foodres.2015.12.003

Lactobacillus acidophilus NCFM was found to increase the production of transient radicals during growth in a 1:1 mixture of brain heart infusion broth and de Man–Rogosa–Sharpe broth as detected by electron spin resonance (ESR) spectroscopy using spin trapping. During growth of L. acidophilus NCFM addition of quercetin, rutin or a whey protein hydrolysate, normally all with antioxidant activity, further increased formation of transient radicals. Such increase in the level of radicals in the growth medium did not have an adverse effect on the viability of L. acidophilus NCFM, but may be involved in inhibition of pathogenic bacteria by L. acidophilus. Catalase decreased the production of radicals without effect on the growth of the catalase-negative L. acidophilus NCFM, whereas superoxide dismutase had no effect on radical production, but hampered bacterial growth. The effect of catalase may be explained by non-radical removal of hydrogen peroxide otherwise being a precursor for hydroxyl radicals formed by transition metal catalysis. Metal ion concentrations decreased in the medium during bacterial growth, which may be the result of transport across bacterial membranes of redox active metal ions like iron and copper chelated by the antioxidant competing with reductive cleavage of hydrogen peroxide forming hydroxyl radicals. Antioxidants may accordingly promote probiotic effect of catalase-negative bacteria through increased formation of reactive oxygen species.
•Lactobacillus acidophilus NCFM produces reactive radicals externally during growth.•Rutin and quercetin, but not antioxidative peptides, stimulate radical production.•Production of external radicals is not affecting viability of L. acidophilus NCFM.•Catalase reduces radical production by L. acidophilus NCFM showing that H2O2 is involved.•Added superoxide dismutase is bacteriostatic towards L. acidophilus NCFM.