1. Composition and structure of the yeast cell wall - YeaMOS
Angel yeast cell wall YeaMOS is a prebiotic composed mainly of mannan-oligosaccharides (MOS) and β-glucans derived from the cell wall of Saccharomyces cerevisiae. Saccharomyces cerevisiae, a natural yeast product commonly found in aquafeeds, contains a variety of immune-boosting compounds, such as mannan, β-glucan, nucleic acids, nucleotides, and chitin, which are capable of improving animal growth by enhancing immune responses and relieving stress (Li and Gatlin, 2006; Zhang et al., 2020; Jin et al., 2018; Abass et al., 2018). The main components of the yeast cell wall are 85-90% polysaccharides, 10-13% proteins, and a small amount of fats and other substances (Osumi 2012). In the aquaculture industry, yeast cell walls have been used as feed additives in fish feeds, with positive effects on growth performance, immune system, health status, disease resistance, gut health and microbiota regulation in fish (Abu-Elala et al., 2018; Guerreiro et al., 2018).
The active components of yeast cell wall are mainly composed of β-Glucan, MOS, glycoprotein and chitin. The content of main components in the YeaMOS (Table 1).
2. Application of YeaMOS in aquaculture
Different types of immune enhancers have been widely used in aquatic animal feeds to enhance innate immunity and disease resistance in aquatic animals. Immunostimulants are naturally occurring substances that mainly act on the immune mechanism of aquatic animals to activate their own immune response, thus providing defense against pathogenic microorganisms (Nawaz et al., 2018). The quality of the immunostimulants provided plays a crucial role in enhancing the immune response. Monsef Shokri et al. found that the addition of 0.5% ImmunoWall, a commercial YCW prebiotic, enhanced the antioxidant effect in Persian sturgeon (Acipenser persicus) (Monsef et al., 2021). Similar to the results of this study, the addition of brewer's yeast cell wall in the range of 1-2 g/kg in Japanese seabass (Lateolabrax japonicus) improved its growth performance and immunity, and increased the cumulative survival rate after virulence by Aeromonasveronii (Yu et al., 2014). Addition of 0.2% YCW to tilapia feed improves non-specific immune responses (phagocytosis, lysozyme activity), up-regulates expression of immune-related genes, and enhances disease resistance (Abu-Elala et al., 2018). In addition, Wang et al. reported that the addition of 0.2% and 0.4% YeaMOS extracts to the feed could improve the growth, immunity and intestinal health of turbot, could reduce the toxic effects of vomitoxin on turbot, and could be used as an effective strategy to control the contamination of feed with vomitoxin (Wang et al., 2021). Similarly, in a 102-day growth study, feeding 0.1% and 0.5% YCW to pacific white shrimp (Litopenaeus vannamei) increased growth and survival rates (Servin et al., 2021). However, the addition of 1 and 2 g/kg of inactive YeaMOS had no significant effect on the growth of pacific white shrimp (Chotikachinda et al., 2008). In a report by Yang et al. on the feeding of aflatoxin-contaminated diets to turbot, it was found that the addition of 0.2% and 0.4% YeaMOS extracts to the diets could be used as a mycotoxin mitigation strategy as well as an effective restoration of the immune response, counteracting the liver damage and the destruction of the intestinal microbiota, and decreasing the aflatoxin residues in the turbot tissues (Yang et al., 2020). In addition, the addition of YCW to aflatoxin-contaminated feeds can reduce aflatoxin poisoning symptoms in tilapia (Tengjaroenkul et al., 2007). In a study of feeding different forms of YeaMOS, it was found that feeding all forms of YeaMOS did not increase the growth of silver gibel carp (Carassius auratus gibelio), but the addition of 0.4% YeaMOS (consisting of 25.64% BG and 25.02% MOS) increased the resistance of silver gibel carp to bacterial attack to a certain extent (Zhang et al., 2020).
3. Optimal addition ratio of YeaMOS to aquaculture
There are many species of aquatic animals and the optimal ratio for adding yeast cell walls varies by species. The best effect of adding 0.67% YeaMOS to the feed of pacific white shrimp can increase the activity of ACP and ALP in serum, muscle and hepatopancreas (Chen et al., 2004). Adding 0.4% YeaMOS to eel feed has the best effect, and it can improve the lysozyme activity in serum (Xiao et al., 2006). The optimal proportion of YeaMOS in the feed of silver crucian carp is 1%, and 8% in the feed of channel catfish and grass carp, which can improve the level of immune response and enhance the ability to resist germs infection. (Luo et al., 2007; Wang and Chen 2008; Chen et al., 2013). Adding 5% YeaMOS to the feed of Chinese softshell turtle has the best effect, and it has obvious promotion effect on non-specific immune function (Wang et al., 2006). For Mississippi paddlefish (Polyodon spathula), adding 10% yeast cell wall to the diet is the most effective, which can enhance leukocyte phagocytosis activity and lysozyme activity (Chen et al., 2014).
YeaMOS is produced by Angel Yeast from brewer's yeast by liquid fermentation of the bacterium, and then by autolysis or exogenous enzyme-catalyzed hydrolysis, or mechanical crushing, the separation of the cell wall obtained by the concentration of the product or drying. It has the effect of improving the non-specific immunity of the organism, and as an immune enhancer, it can well improve the current situation of healthy aquaculture of aquatic products, and it has a very broad application prospect in the modern aquaculture industry with high incidence of diseases and diversified sources of stress.
About Angel Animal Nutrition
Fubon is a brand of Angel Animal Nutrition. Fubon is committed to developing natural, efficient microbial feed derived from yeast with Angel's leading technology in yeast industry, providing the best service solutions for the nutrition and health in animals. Angel Animal Nutrition creates value for global feed and animal agriculture customers through continuously upgraded products and professional services.
About Angel
Angel Yeast Company is a high-tech listed company specializing in yeast and biotech. Product business covers Yeast and Baking, Yeast Extract-Savoury, Nutrition & Health and Biotechnology fields. It is one of the world's leading companies in the yeast industry. Angel has 12 holding subsidiaries and provides products and services for more than 150 countries and regions.
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