Structural identification and immunostimulatory effect of Bacillus velezensis GV1 polysaccharides via TLR4/NF-κB signaling pathway in RAW264.7 macrophages

Microbial polysaccharides derived from bacterial sources possess unique properties because of their structural complexity contributing to exceptional characteristics, including potent immunostimulatory effects. In this study, we extracted crude polysaccharide from Bacillus velezensis GV1 (BPS) which was isolated from Korean ginseng vinegar, and subsequently characterized for sugar composition and functional groups using FT-IR and methylation method. Structural analysis indicated that BPS was composed of mannan and glucan in a ratio of 7.5:2.5. The immunostimulatory effect of BPS was investigated in RAW264.7 macrophages. The results revealed that BPS significantly increased NO production, as well as the secretion and expression of key cytokines, such as IL-6, TNF-alpha, and IL-1 beta. These effects were confirmed using a TLR4 antagonist (TAK-242). Moreover, BPS exhibited immunostimulatory potential by promoting the NF-kappa B signaling pathway. In conclusion, this study establishes a foundation for the potential application of BPS as an immunostimulatory adjuvant or alternative component in functional foods, particularly for enhancing innate immune responses.