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.
Highlights
Soy sauce is one of the best known soy products worldwide, its production methodology varies significantly depending on the country
Polysaccharides are usually extracted from plants, and many plant-derived polysaccharides have non- or less toxicity and few side effects (Nie et al, 2019)
We found that all four polysaccharide fractions consisted of neutral sugar (56~62%), uronic acid (30~35%), and a small amount of proteins and polyphenols
Summary
Soy sauce is one of the best known soy products worldwide, its production methodology varies significantly depending on the country. In a previous study on signaling pathway, it was observed that plant-derived polysaccharides usually recognize and bind to pattern recognition receptors on the surface of macrophages and activate them These polysaccharides in turn activate intracellular signaling pathways, including mitogen-activated protein kinases (MAPK) and nuclear factor kappa-light-chain-enhancer of activated B cells (NK-κB) pathways, leading to regulation of the immune system via secretion of cytokines, enzymes (iNOS and COX-2), and chemokines (Kim et al, 2019). In this present study, we isolated and purified polysaccharides from different types of soy sauce and analyzed their chemical properties. We investigated their macrophage-stimulating activities by evaluating the production of NO and cytokines in peritoneal macrophages, and further, showed the activation of signaling pathways using RAW 264.7 cells
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