The Function And Role Of Yeast Cell Wall

Research has shown that yeast cell walls can stimulate the immune function and disease resistance of animal bodies, participate in and promote the release of inflammatory cytokine TNF - α, and participate in the release of other cytokines such as 1L-1, 1L-2, and 1L-6. Its function mainly relies on the unique functions of β - glucan and mannan.
β - glucan
The β - glucan in yeast cell wall has immune regulatory function, which is related to its unique triple helix structure. There are some hydrophilic groups on the outer side of the helix, which is a non-specific immunostimulatory polysaccharide that can specifically bind to the body's immune cell receptors, stimulate B cells, T cells, and natural killer cells to produce a large number of macrophages, and thus regulate the body's immunity. β - glucan exerts physiological functions through macrophages: firstly, it enhances phagocytic function; The second is to promote specific immune responses through the antigen presentation of macrophages; Thirdly, activated macrophages can secrete various bioactive substances, such as TNF - α, 1L-1, NO, reactive oxygen species, etc. Among them, 1L-1 and NO are important immune regulatory factors with antiviral, antibacterial, and anti-tumor activities. TNF - α has the effects of increasing the permeability of vascular epithelial cells, promoting the aggregation of immune effector molecules, and stimulating the release of other inflammatory cytokines.
Xu Junfa et al. [2] pointed out that yeast polysaccharides are an immunomodulatory agent that can induce mouse peritoneal macrophages to produce 1L-1 and NO. Suzuki et al. found that β -1,3-glucan and β -1,6-glucan can enhance the host's anti-tumor and anti pathogenic microbial functions by activating macrophages, stimulating T cells to differentiate into helper Th1 cell subsets. Kong Weihua et al. pointed out that β - glucan is an important immune enhancer for the digestive tract mucosa. As is well known, macrophages are important tissue repair guiding cells, and neutrophils are important anti infective cells. Both types of cells contain beta-1,3-glucan receptors on their surface, which are effector cells of β - glucan. β - glucan activates macrophages (tissue repair) and neutrophils (anti infection) in gastrointestinal tissues, activates the "immune neuroendocrine" regulatory network, enhances cell anti stress and anti infection abilities, strengthens the tissue repair function of macrophages, and accelerates ulcer repair. Hiss S et al. found that β -1,3-glucan can also serve as an immune adjuvant to stimulate antibody production. The research results indicate that β - glucan (extracted from yeast cell wall) has significant immune function in weaned piglets and can significantly increase the titer of blue ear disease antibodies in piglets. Figueras A et al. studied the efficacy of yeast β - glucan as a vaccine immune adjuvant. The experiment showed that when glucan was used as an immune adjuvant, the different order of vaccine and adjuvant use would affect the immune effect; Injecting glucan after vaccination has a better effect.
The antioxidant function of β - glucan indicates that yeast β - glucan can inhibit the peroxidation reaction of phosphatidylcholine liposomes caused by OH, significantly reducing the formation of conjugated diene bonds. Carboxymethylated β -1,3-glucan also has the function of scavenging free radicals and exhibits significant antioxidant activity. According to the measurement of carboxyl content in the plasma of mice with arthritis after injection of carboxymethyl glucan, the degree of tissue oxidation in mice was alleviated, which provides a new idea for the application of carboxymethyl glucan in the treatment of arthritis diseases.
Other biological functions of β - glucan. A review shows that β -1,3-glucan in animal digestive tract is non absorbable, insoluble, and does not produce viscosity. It can clean the intestine, eliminate free radicals, dissolve cholesterol, prevent hyperlipidemia, and resist infections caused by filtering bacteria, fungi, viruses, etc. In addition, β -1,3-glucan is a low calorie food additive, which can significantly reduce the glucose content in the blood, control obesity, and prevent diabetes and cardiovascular disease.
Mannan
The two confirmed functions of mannan in yeast cell wall products are to adsorb pathogenic bacteria and regulate immunity. The key to intestinal pathogen infection is the ability to successfully adhere to the intestinal mucosa. The mechanism of adhesion is that exogenous lectins on the flagella or villi of the pathogen can specifically recognize and bind to receptors on the host epithelial cell membrane. Mannan mainly exerts antibacterial functions through two aspects: firstly, it interferes with the colonization of intestinal pathogens. The principle is that the specific receptors of pathogenic bacteria on the intestinal wall are structurally similar to mannan. If there is a rich source of mannose in the intestine, it can bind to the specific receptors of pathogenic bacteria, preventing them from attaching to the intestinal wall and effectively inhibiting infection. After the combination of pathogens and mannan, they cannot use mannan as an energy source for their growth. Therefore, mannan has a dual effect of preventing the colonization and reproduction of pathogens, and is also known as a "pathogen adsorbent" or "pathogen scavenger". Secondly, mannan can serve as a nutrient for beneficial bacteria (such as bifidobacteria, lactobacilli, etc.) in the intestine, promoting the proliferation of beneficial bacteria and further inhibiting the growth of harmful bacteria. According to Alitech, mannan can be selectively fermented and utilized by beneficial bacteria such as Bifidobacterium and Lactobacillus, promoting their growth and reproduction, producing acetic acid and lactic acid, leading to a decrease in intestinal pH, further inhibiting the growth and reproduction of harmful bacteria such as Clostridium perfringens, and thus playing a bacteriostatic role. Research by Yan Guiling and others has shown that beer yeast mannan can promote the growth of beneficial bacteria and increase the content of volatile fatty acids in the intestine.
The immune regulatory function of mannan is mainly reflected in its ability to enhance cytokine release and interferon activity, promote or coordinate the activity of different immune cells, enhance the migration of white blood cells to the site of infection, and activate macrophages. Che et al. found that adding mannan to the diet of weaned piglets infected with porcine reproductive and respiratory syndrome virus can significantly reduce the TNF - α content in piglet serum, increase IL-1 content and lymphocyte count, thereby ensuring pig health; Eicher et al. found that mannan can alleviate bacterial infections in weaned piglets, regulate innate immunity, and promote piglet growth.
Mannan can also activate immune response. When used together with vaccines, it can bind to certain viruses, toxins, and eukaryotic cells. The bound mannan acts as an exogenous antigen adjuvant, which can alleviate antigen absorption and increase antigen potency. Therefore, as an adjuvant, mannan can enhance the body's cellular humoral immunity. In addition, mannan can stably adsorb various fungal toxins through intermolecular forces such as hydrogen bonding and van der Waals forces, forming polysaccharide toxin complexes that prevent toxins from being absorbed by the intestine. Its unique spatial structure also provides more sites for toxin binding. Swamy H et al. found that mannan can alleviate the adverse effects of aflatoxin on daily weight gain and feed intake in broiler chickens, and reduce the risk of organ swelling.
Energy effect
Glucan and mannan can be fermented and utilized by intestinal bacteria such as bifidobacteria in the large intestine, producing short chain fatty acids. Part of short chain fatty acids are utilized and converted into energy by colonic mucosal epithelial cells, while the other part is transferred to the liver for utilization. The above functions can also increase the content of organic acids, reduce the production of spoilage substances, and lower the emissions of ammonia and hydrogen sulfide.