納豆枯草桿菌NTU-18對於南美白對蝦生長、腸道菌相與免疫相關基因表達的影響

Abstract

白蝦 (Litopenaeus vannamei) 是目前全球產量最大的甲殼類養殖物種，面對高飼料成本、自然資源枯竭與疾病爆發等多重挑戰。因此，學界與業界聚焦於改善飼料效率與降低環境風險，其中益生菌的應用為最具潛力的解決方案之一。枯草芽孢桿菌 (Bacillus subtilis) 具備抗逆境能力強、消化酶活性及抑菌能力等優勢，且新菌株功能性研究仍持續進行。先前研究證實 B. subtilis natto NTU‑18 菌株可有效提升烏魚 (Mugil cephalus) 及日本鰻 (Anguilla japonica) 的生長與免疫表現。為探討該菌株於白蝦養殖之潛力，本研究設置空白對照組與添加濃度分別為 0.1%、0.5% 及 2% 的三個處理組，每組各三重複，進行為期 35 天的養殖實驗，透過成長表現、血球免疫基因表現及腸道菌相分析，評估其應用效果。結果顯示，0.5% 組在 FBW、WGR 及 FCR 上均有顯著提升 (p < 0.05)。血球免疫基因表現方面，0.5% 及 2% 組的 Lysozyme 與 LGBP 表現量低於對照組，顯示當添加濃度達一定水平，可減緩病原侵擾；此外，serine proteinase (proPO的前驅物) 在所有添加組中顯著高於對照組 (p < 0.05)，而 proPO 水準則維持一致，顯示免疫系統提升準備並維持良好調節能力。腸道菌相上，各添加組的 α‑diversity 均呈上升趨勢，且 2% 組 Shewanella 屬豐度顯著增加。綜合上述結果，適量添加 B. subtilis natto NTU‑18 可降低免疫應激、改善腸道菌相，並進而提升白蝦生長表現。

White shrimp (Litopenaeus vannamei) is the most widely farmed crustacean species globally, facing multiple challenges such as high feed costs, depletion of natural resources, and disease outbreaks. So, researchers and the industry are focusing on improving feed efficiency and reducing environmental risks, with the use of probiotics being one of the most promising solutions. Bacillus subtilis is resistant to tough conditions, helps with digestive enzyme activity, and has antibacterial properties, with research into the functions of new strains still going on. Previous research has confirmed that the B. subtilis natto NTU-18 strain can effectively improve the growth and immune performance of Mugil cephalus and Anguilla japonica. To explore the potential of this strain in white shrimp farming, this study set up a blank control group and three treatment groups with concentration levels of 0.1%, 0.5%, and 2%, each with three replicates, and conducted a 35-day farming experiment to evaluate its application effects through growth performance, hemolymphocyte immune gene expression, and intestinal microbiota analysis. The results showed that the 0.5% group had significantly higher FBW, WGR, and FCR (p < 0.05). In terms of hemolymphocyte immune gene expression, the expression levels of lysozyme and LGBP in the 0.5% and 2% groups were lower than those in the control group, indicating that when a certain concentration level is added, the invasion of pathogens can be reduced. Additionally, serine proteinase (the precursor of proPO) was significantly higher in all probiotic-added groups compared to the control group (p < 0.05), while proPO levels remained consistent, indicating that the immune system is enhanced and maintains good regulating capacity. In terms of gut microbiota, α-diversity increased in all probiotic-added groups, and the abundance of the genus Shewanella significantly increased in the 2% group. In summary, appropriate addition of B. subtilis natto NTU-18 reduces immune stress, improves gut microbiota, and further enhances the growth performance of white shrimp.