Candida utilis yeast as a functional protein source for Atlantic salmon (Salmo salar L.): Local intestinal tissue and plasma proteome responses

Abstract

Microbial ingredients such as Candida utilis yeast are known to be functional protein sources with immunomodulating effects whereas soybean meal causes soybean meal-induced enteritis in the distal intestine of Atlantic salmon (Salmo salar L.). Inflammatory or immunomodulatory stimuli at the local level in the intestine may alter the plasma proteome profile of Atlantic salmon. These deviations can be helpful indicators for fish health and, therefore potential tools in the diagnosis of fish diseases. The present work aimed to identify local intestinal tissue responses and changes in plasma protein profiles of Atlantic salmon fed inactive dry Candida utilis yeast biomass, soybean meal, or combination of soybean meal based diet with various inclusion levels of Candida utilis. A fishmeal based diet was used as control diet. Inclusion of Candida utilis yeast to a fishmeal based diet did not alter the morphology, immune cell population or gene expression of the distal intestine. Lower levels of Candida utilis combined with soybean meal modulated immune cell populations in the distal intestine and reduced the severity of soybean meal-induced enteritis, while higher inclusion levels of Candida utilis were less effective. Changes in the plasma proteomic profile revealed differences between the diets but did not indicate any specific proteins that could be a marker for health or disease. The results suggest that Candida utilis does not alter intestinal morphology or induce major changes in plasma proteome, and thus could be a high-quality alternative protein source with potential functional properties in diets for Atlantic salmon.

Effects of Yeast Species and Processing on Intestinal Health and Transcriptomic Profiles of Atlantic Salmon (Salmo salar) Fed Soybean Meal-Based Diets in Seawater

“…Yeasts are gaining increasing interest as alternative ingredients for salmonids [12][13][14]. Yeasts are not only high-quality protein ingredients but also contain bioactive components that have the potential to mitigate SBMIE in Atlantic salmon [15][16][17]. The yeast cell wall contains bioactive components, including β-glucan, mannan and chitin, which has immune-modulating properties that reduce inflammation caused by SBM [15].…”

Impact of high dietary plant protein with or without marine ingredients in gut mucosa proteome of gilthead seabream (Sparus aurata, L.)

“…Proteome alterations on gut, skin or even plasma proteome caused by high dietary plant protein inclusion have been reverted thanks to some dietary additives, such as Candida utilis yeast [41] or sodium butyrate [38], in turns improving the fish performance and the immune status [42,43]. In this sense, marine alternative ingredients with potential functional properties, such as krill and squid meal, can be an interesting option to improve plant-based diets for carnivorous fish, reducing the inclusion of synthetic dietary supplements such as synthetic amino acids or minerals, and providing an optimal nutrient efficiency and economic profit ratio [44].…”

Torula Yeast in the Diet of Atlantic Salmon Salmo Salar and the Impact on Growth Performance and Gut Microbiome.

“…Conversely, when torula yeast is added to a mix of protein sources it is more effective for growth performance and promoting desirable gut bacteria at moderate levels of 10% inclusion than at the higher inclusion level of 20%. The nding that moderate levels of torula yeast in a mixed protein diet are preferable to higher inclusions is re ected in the existing literature for Atlantic salmon (Salmo salar) 21 . It should be noted that this study sampled the gut digesta and mucosa together, which may have masked further differences in the gut microbiome community composition, since the digesta appears most impacted by diet.…”

“…Torula yeast has displayed bene cial functional properties such as a reduction in in ammation of the distal intestine during smolti cation, a crucial developmental period for Atlantic salmon 14 . Torula yeast has also been associated with immune-modulating bene ts which could greatly enhance their value to the aquaculture industry 21 . However, a signi cant research gap exists in optimising and standardising the dietary inclusion levels which is necessary to facilitate commercial adoption of this alternative protein 22 .…”