The Chinese mitten crab (Eriocheir sinensis) is an important component in Chinese aquaculture. Due to its lacking adaptive immune system as a crustacean, it exhibits poor tolerance to environmental stresses, particularly the deleterious impact of lipopolysaccharide (LPS) from pathogenic bacteria during E. sinensis culture. In a previous study, we isolated LGSPDVIVIR (cmP4) peptide from cottonseed meal hydrolysate, having excellent antioxidant and immune-enhancing properties in vitro. Expressing this peptide abundantly as a tandem (a tandem of five cmP4 peptides, cmP4') using the Bacillus subtilis expression system, we aimed to investigate the effects of incorporating recombinant B. subtilis into diets on growth performance, acute oxidative stress, and hepatopancreatic injury induced by LPS injection in E. sinensis. Crabs were cultured for a period of 12 weeks on three diets: basal diet, basal diet supplemented with 10