Polysaccharide isolated from Korean-style soy sauce activates macrophages via the MAPK and NK-κB pathways

Abstract Soy sauce is a staple fermented food in Korea, however, there are relatively limited studies on soy sauce in Korea compared to that in Japan. In this study, the immuno-stimulating activities are compared in polysaccharides isolated from soy sauce in Korea and Japan. Crude polysaccharides was isolated, and which were named as Korean-style soy sauce (KSS-0) and Japanese-style soy sauce (JSS-0). Then, difference in cytokine production was compared in peritoneal macrophages, and KSS-0 showed higher cytokine production than JSS-0. The KSS-0 was purified into two polysaccharides, which were named as KSS-I and KSS-II. The polysaccharides consisted mainly galacturonic acid, xylose, and galactose. Out of the four polysaccharides isolated, KSS-II enhanced NO and cytokines production the most. Western blot analysis showed that KSS-II phosphorylated the MAPKs and nuclear factor NF-κB in RAW 264.7 cells in a dose-dependent manner. These results suggested that KSS-II activates macrophages via the MAPK and NF-κB pathways, and also induces an increase in the cytokine production. In conclusion, the polysaccharides isolated from Korean soy sauce have better immune-stimulating activities than those from Japan and may be used as potential functional foods.