Antioxidant activity and short-chain fatty acid production of lactic acid bacteria isolated from Korean individuals and fermented foods

Abstract

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. <i>Bifidobacterium bifidum</i> MG731 showed the high 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity (90.6%), followed by <i>Bifidobacterium lactis</i> MG741 (59.6%). The <i>Bi. lactis</i> MG741 showed the high ABTS free radical scavenging activity (99.5%), followed by <i>Lactobacillus plantarum</i> MG989 (98.9%), <i>Lactobacillus salivarius</i> MG242 (97.1%), and <i>Bi. bifidum</i> MG731 (96.1%). In addition, <i>Bi. bifidum</i> MG731 showed the lowest nitric oxide production (4.28 µM), followed by <i>B. lactis</i> MG741 (10.80 µM), <i>L. salivarius</i> MG242 (14.60 µM), and <i>L. plantarum</i> 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 <i>Bi. bifidum</i> MG731 showed total SCFAs production (4998.6 µg/g), <i>Bi. lactis</i> MG741 (2613.9 µg/g), <i>L. salivarius</i> MG242 (1456.1 µg/g), and <i>L. plantarum</i> 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.