Effect of hydrogen peroxide on the dehydrogenase and quinone-reductase activity of irradiated Lactobacillus plantarum cells

Abstract

The resistance of lactobacilli to oxidative stress is of great importance for their applicability as probiotics. This study aimed to evaluate the response of Lactobacillus plantarum strain ATCC® 14917™, grown in either de Man, Rogosa, and Sharpe agar (MRS medium) or tryptic soy broth (TSB medium), to 1–2 mM H2O2 after the exposure to different doses of ionising radiation. Two bacterial extracellular enzyme groups, dehydrogenases (DHAs) and quinone reductases (QRs), served as the criteria of viability and antioxidant activity, respectively. The irradiated L. plantarum culture grown in TSB showed increased QR activity at irradiation doses of 2–50 Gy, with the maximum activity at 10 Gy, compared to non-irradiated cells. The QR activity of the MRS-grown culture was increased significantly (p < 0.05) in the presence of H2O2 for the cells subjected to irradiation, compared to the control. The cultivation of L. plantarum in TSB resulted in considerable morphological changes in the 24 h culture. Our results indicate that the cultivation of L. plantarum in TSB activated the antioxidative potential of these bacteria. The most important aspect of this phenomenon is the extracellular enzyme activity that may directly influence the host organism by providing antioxidant activity.