Effects of yeast species and processing on transcriptomic profile and intestinal health of Atlantic salmon (Salmo salar) fed soybean meal-based diets in seawater

The objective of the current study was to examine the effects of yeasts on intestinal health and transcriptomic profile of Atlantic salmon fed SBM-based diets in seawater. Cyberlindnera jadinii (CJ) and Wickerhamomyces anomalus (WA) yeasts were produced in-house and processed by direct heat-inactivation with spray-drying (ICJ and IWA) or autolyzed at 50 ºC for 16 h (ACJ and AWA), followed by spray-drying. Six diets were formulated, one based on fishmeal (FM), a challenging diet with 30% soybean meal (SBM) and four other diets containing 30% SBM and 10% of each of the four yeast fractions (i.e., ICJ, ACJ, IWA and AWA). The results showed that the inclusion of CJ yeasts reduced loss of supranuclear vacuolization, along with reduction in population of CD8a positive cells present in the lamina propria of fish fed the SBM diet. The CJ yeasts controlled the inflammatory profile of fish fed SBM through up-regulation of pathways related to wound healing and taurine metabolism. Additionally, the WA yeasts dampened the inflammatory profile of fish fed SBM through down-regulation of pathways related to toll-like receptor signaling, C-lectin receptor, cytokine receptor and signal transduction. The results suggest that yeasts could be used as protein ingredients with functional properties in diets for Atlantic salmon. Overall design: Examination of intestinal health of Atlantic salmon fed diets containing four different yeast treatments.

本研究旨在探究海水养殖条件下，饲喂豆粕（Soybean Meal, SBM）基础饲料的大西洋鲑，其肠道健康与转录组谱受酵母的调控效应。本研究自制耶氏酒香酵母（Cyberlindnera jadinii, CJ）与异常威克汉姆酵母（Wickerhamomyces anomalus, WA），并通过两种工艺进行处理：其一为直接热灭活联合喷雾干燥（对应组分分别记为ICJ与IWA），其二为于50℃下自溶16小时后再进行喷雾干燥（对应组分分别记为ACJ与AWA）。共设计6组实验饲料：1组以鱼粉（Fishmeal, FM）为唯一蛋白源的基础饲料，1组添加30%豆粕的应激对照饲料，以及4组同时添加30%豆粕与10%四种酵母组分（ICJ、ACJ、IWA、AWA）的实验饲料。实验结果表明，相较于单纯饲喂SBM饲料的大西洋鲑，添加CJ酵母可减轻其肠黏膜固有层的核上空泡化现象，并降低固有层内CD8a阳性细胞的数量；CJ酵母还可通过上调伤口愈合与牛磺酸代谢相关通路，调控饲喂SBM饲料的鲑鱼炎症状态。此外，WA酵母可通过下调Toll样受体（Toll-like receptor）信号通路、C型凝集素受体、细胞因子受体及信号转导相关通路，缓解饲喂SBM饲料的鲑鱼炎症反应。本研究结果提示，酵母可作为具备功能特性的蛋白原料应用于大西洋鲑配合饲料。总体实验设计：对饲喂含四种不同酵母处理组分饲料的大西洋鲑肠道健康进行评估。