Seaweed-associated Bacillus megaterium DSKPDF CMST3 was screened for EPS production and its production was statistically optimized using central composite design and response surface methodology. Structural characterization of EPS was investigated by FT-IR and NMR spectroscopy. Furthermore, morphological structure of the EPS investigated by SEM demonstrated it to be less porous with flake-like structure. The XRD and TGA observations revealed the semi-crystalline nature of EPS. EPS-supplemented diet significantly enhanced immunological and hematological parameters in Labeo rohita. The immune gene expression (IL10, IL-1β, and TGFβ) were significantly upregulated in lymphoid organs of the fish. Moreover, the dietary supplementation of EPS showed significantly (p < 0.001) higher survival rates of DII (71%) compared with basal diet (56.40%) fed fish against Aeromonas hydrophila infection. The result suggests that the exopolysaccharide can be applied as a fish feed supplement to enhance fish immunity and disease resistance against A. hydrophila.

筛选海藻相关巨大芽孢杆菌DSKPDF CMST3 的 EPS 生产，并使用中心复合设计和响应面方法对其生产进行统计优化。通过 FT-IR 和 NMR 光谱研究 EPS 的结构表征。此外，通过 SEM 研究的 EPS 的形态结构表明它的多孔性较小，具有片状结构。XRD 和 TGA 观察揭示了 EPS 的半结晶性质。补充 EPS 的饮食显着提高了Labeo rohita的免疫学和血液学参数。免疫基因表达（IL10、IL-1β 和 TGFβ）在鱼的淋巴器官中显着上调。此外，EPS的膳食补充剂显着（p < 0.001) 与基础日粮 (56.40%) 相比，DII 的存活率 (71%) 更高，以抵抗嗜水气单胞菌感染的鱼。结果表明，胞外多糖可作为鱼饲料补充剂，增强鱼对A.hydrophila的免疫力和抗病能力。