Intracellular pyruvate as one of the major bioactive substances of lactic acid bacteria isolated from kimchi

The present study aimed to identify the metabolites associated with the physiological activity of kimchi-derived lactic acid bacteria (LAB). A clear difference was observed between the 2,2 '-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging rates when the pyruvate content was high (273.5 ng/mu L; radical removal speed 6.50% per min) and the rates when the pyruvate content had decreased (131.9 ng/mu L; radical removal speed 3.63% per min). Additionally, the characteristics of LAB antioxidant activity (increase in ABTS radical scavenging activity with reaction time, low level of 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity) were similar to those of pyruvate-derived activity. Hydrogen peroxide content (WiKim0124, 2.08 -> 0.26; WiKim0121, 0.99 -> 0.47; WiKim39, 1.93 -> 0.24) and lactate dehydrogenase activity (WiKim0124, 1.53 -> 0.00; WiKim0121, 0.73 -> 0.01; WiKim39, 1.72 -> 0.02) decreased more in heat-killed LAB than in non-heat-killed LAB. Accordingly, this resulted in increased pyruvate content and the inhibitory activity of lipid peroxide production increased by 2-3 times. Our findings indicate that pyruvate is one of the major metabolites regulating LAB physiological activity.