Immunostimulatory Effects of Exopolysaccharide Produced by Mangrove Habitat Actinobacterium, Isolated From the Marine Environment of Tuticorin

In our present study, the evaluation was done on immunostimulatory activity of the exopolysaccharide (EPS) derived from a marine actinobacterium, Streptomyces sp. SRT21. The average molecular weight (Mw) of purified SRT21-EPS was estimated to be 2.86 × 10⁵ Da. NMR analysis demonstrated the incidence of α-(1–3) glycosidic linkage of glucose and frequency of mannose with α-(1–6) glycosidic linkage. The structural pattern of SRT21-EPS was peaked in the range of 22.8° and 43.5° at 2θ in XRD, while the ZP value was detected as −11.7 mV. The thermal behaviour of SRT21-EPS was characterized by DTA and TGA. In SEM, the morphology of SRT21-EPS were observed as irregular, branchy and flake-based polymeric matrix. With optimal dosage, SRT21-EPS promoted the cell proliferation, Nitric oxide (NO) levels induction, phagocytosis index and ROS production in macrophage cells. As a result, the key pro-inflammatory cytokines secretion, IκB-α degradation and nuclear localization of p65 was accomplished through TLR receptor/NF-κB signaling.