Oxidative stress, which can cause imbalance in the body by damaging cells and tissues, arises from the immoderate production of reactive oxygen species (ROS)/reactive nitrogen species (RNS). Therefore, external supplements having antioxidant activity are required for reducing oxidative stress. In our study, we investigated DPPH and ABTS radical scavenging ability, and the inhibition effect on the nitric oxide (NO) production of 15 food-derived bacterial strains in LPS-activated RAW264.7 cells. Among these LAB strains, eight strains with an excellent inhibition effect on NO production were selected through comparisons within the same genera. Moreover, the selected strains, including Leuconostoc mesenteroides MG860, Leu. citreum MG210, Pediococcus acidilactici MG5001, P. pentosaceus MG5078, Weissella cibaria MG5090, Levilactobacillus brevis MG5306, Latilactobacillus curvatus MG5020, and Latilactobacillus sakei MG5048 diminished the inducible nitric oxide synthase (iNOS)/cyclooxygenase-2 (COX-2) expression. In addition, the stability and adhesion ability of the eight LAB strains in the gastrointestinal tract were determined. In conclusion, the selected strains have potential as new probiotics with antioxidant effects.

Compounds of the cell walls of heat-killed lactic acid bacteria show immunomodulatory properties which boost immunological systems, and are used ad postbiotics (paraprobiotics). In this study, we used 17 different heat-killed isolates as postbiotics and evaluated their anti-inflammatory potential on the expression of proinflammatory mediators and cellular signaling pathways of murine macrophage, RAW 264.7 cells. Bifidobacterium bifidum MG731 showed the high 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity (90.6%), followed by Bifidobacterium lactis MG741 (59.6%). The Bi. lactis MG741 showed the high ABTS free radical scavenging activity (99.5%), followed by Lactobacillus plantarum MG989 (98.9%), Lactobacillus salivarius MG242 (97.1%), and Bi. bifidum MG731 (96.1%). In addition, Bi. bifidum MG731 showed the lowest nitric oxide production (4.28 µM), followed by B. lactis MG741 (10.80 µM), L. salivarius MG242 (14.60 µM), and L. plantarum MG989 (19.60 µM). The selected strains showed a decreased nitric oxide production via downregulation of inducible nitric oxide synthase and cyclooxygenase 2, which were upregulated via LPS-stimulated RAW 264.7 macrophages. Short-chain fatty acids (SCFA) including acetic, propionic, and butyric acid were produced by four strains. The Bi. bifidum MG731 showed total SCFAs production (4998.6 µg/g), Bi. lactis MG741 (2613.9 µg/g), L. salivarius MG242 (1456.1 µg/g), and L. plantarum MG989 (630.2 µg/g). These results indicated that the various selected strains may possess an anti-inflammatory potential and provide a molecular basis for the development of functional probiotics.