ASSESSING ANTIOXIDANT AND PROOXIDANT PROPERTIES OF LACTOBACILLI AND ENTEROCOCCI STRAINS BY USING ORAC AND LUX-BIOSENSOR METHODS

Lactobacilli are widely used in medicine as probiotic bacteria. Lactobacilli are considered one of the most important types of intestinal microbes. These bacteria have an antioxidant, gene protective effect on the immune and nervous systems of the host. But some strains of enterococci can be pathogenic microorganisms and cause diseases such as urinary tract infections, bacteremia, infections at the surgical sites, bloodstream infections, diarrhea. The need to study the beneficial and harmful properties of bacteria for humans determines the relevance of the study. The antioxidant and prooxidant properties of 11 Enterococcus strains and 7 metabolites of Lactobacillus strains were analyzed using an oxygen radical absorption capacity (ORAC) analysis and a lux biosensor test. Bacteria were incubated in cow's milk. Unfermented milk was used as a control. A study showed that milk fermented with enterococci did not have significant differences in antioxidant ability compared to control. In contrast, almost all lactobacilli increased the antioxidant ability of sour milk compared to unfermented milk. That is, the metabolites of Lactobacillus strains have demonstrated strong antioxidant properties even at low concentrations. The metabolites of Enterococcus strains possessed prooxidant properties. They enhanced the action of other prooxidants, such as paraquat, hydrogen peroxide, dioxidine, and showed a synergistic effect. The Lux biosensor test, used to evaluate the effect of substances on living cells with a complex metabolism, was more informative than the ORAC analysis, which allowed to evaluate the antioxidant and prooxidant properties of probiotic bacteria metabolites. The study revealed not only the influence of the direct effect of the test substance on the target molecule, but also the effect of indirect action by interfering with other biochemical processes of a living cell, which confirmed the need to use the biosensor lux test for further work when choosing strains of probiotic bacteria.