Probiotics play vital roles in controlling diseases, enhancing specific and non-specific immunity and stimulating growth in the aquaculture industry. However, the effect of fermentation of feed by probiotics on the immune ability of sea cucumber has not been reported to date. Here, three candidate probiotic strains (Bacillus species) were isolated from the culture seawater and sediment of sea cucumber, and fishmeal and scallop mantle fermented by the candidate probiotic strains were used to feed sea cucumber. The results showed that the free amino acid and small peptide contents of the fishmeal and scallop mantle were significantly increased after fermentation for 72 h. However, the weight gain (WG) and specific growth rate (SGR) of sea cucumber showed no significant differences among the fermented fishmeal, fermented scallop mantle and control groups. Scallop mantle fermented by the three candidate probiotics could increase the coelomocyte number and respiratory burst activity. The immune-related enzymatic activity was increased after consuming the fermented fishmeal and scallop mantle, while the activity of antioxidant enzymes was reduced. The expression levels of immune- and antioxidant-related genes were changed after consuming the fermented fishmeal and scallop mantle. Taken together, our results suggest that probiotics could increase the immunocompetence of sea cucumber, and fermented scallop mantle might be a potential substitute for fishmeal during feed preparation. Our results lay a foundation for further understanding the relationship between probiotics and the non-specific immunity of sea cucumber.

益生菌在控制疾病，增强特异性和非特异性免疫力以及刺激水产养殖业增长方面发挥着至关重要的作用。然而，迄今为止尚未报道益生菌发酵饲料对海参免疫能力的影响。在这里，三种候选益生菌菌株（芽孢杆菌从养殖海水和海参的沉积物中分离出海藻，然后用候选益生菌菌株发酵后的鱼粉和扇贝壳饲喂海参。结果表明，发酵72 h后，鱼粉和扇贝披风的游离氨基酸和小肽含量明显增加。然而，海参的增重（WG）和比生长速率（SGR）在发酵的鱼粉，扇贝发酵的披风和对照组之间没有显着差异。三种候选益生菌发酵后的扇贝披风可增加血管内皮细胞数量和呼吸爆发活性。食用发酵的鱼粉和扇贝后，免疫相关的酶活性增加，而抗氧化酶的活性降低。食用发酵鱼粉和扇贝后，免疫和抗氧化剂相关基因的表达水平发生了变化。综上所述，我们的结果表明，益生菌可以提高海参的免疫能力，发酵扇贝披风可能是饲料制备过程中鱼粉的潜在替代品。我们的结果为进一步了解益生菌与海参非特异性免疫之间的关系奠定了基础。