Views: 5 Author: Site Editor Publish Time: 2025-10-11 Origin: Site
Glucans are a class of natural polysaccharides composed of glucose monomers linked by glycosidic bonds. They are widely found in the biological world, including bacteria, fungi, algae, and higher plants. As the most abundant polysaccharide in fungal cell walls, glucans have a highly variable structure, with glucose residues linked by α- or β-glycosidic bonds to form linear or branched structures, exhibiting amorphous or microfibrillar morphologies.
Glucans have attracted considerable attention due to their unique biological activities, with demonstrated benefits such as immunomodulatory, anti-tumor, anti-inflammatory, antioxidant, and lipid- and blood-glucose-lowering properties. These properties hold broad application prospects in the food industry, healthcare, and cosmetics. β-glucans, in particular, are considered highly effective and low-toxic bioresponse effectors due to their ability to activate the innate immune system, enhance macrophage phagocytosis, and regulate cytokine secretion.
Black yeast, scientifically known as Aureobasidium pullulans, is a polymorphic fungus widely distributed on plant surfaces and in soil. It belongs to the Deuteromycetes and the family Aureobasidium. It has a variety of cell morphologies, including yeast-like, hyphae-like, and chlamydospores. It is closely related to yeast and produces two different types of exopolysaccharides during fermentation: pullulan and beta-glucan.
Saccharomyces cerevisiae is a unicellular fungus belonging to the phylum Ascomycota and the family Saccharomyces. It is an important industrial fermentation strain. As one of the earliest microorganisms used by humans, Saccharomyces cerevisiae has a long history of application in food fermentation, biopharmaceuticals, and other fields. Its cell wall is rich in beta-glucan, making it the most extensively studied and widely used source of yeast glucans.
Black yeast and Saccharomyces cerevisiae exhibit significant differences in their microbiological characteristics, which directly affect the properties and yield of the glucans they produce.
Black yeast is a polymorphic fungus with various cell morphologies, including yeast-like, hyphae-like, and chlamydospores. During fermentation, when in the yeast form, black yeast secretes large amounts of beta-glucans. This process occurs when intracellular enzymes convert the carbon source in the culture medium into polysaccharides, which are then secreted extracellularly. The formation of these morphologies is influenced by various factors, including culture medium composition and culture conditions, and can be transformed between the two.
Black yeast has a strong adaptability to various environments and is widely found in forest soils, lakes, plant materials, animal tissues, and even in seafloor mud. This wide distribution enables it to survive and reproduce in a wide range of environmental conditions, facilitating industrial production.
Saccharomyces cerevisiae is a unicellular fungus that primarily exists in a yeast form and reproduces asexually by budding. Unlike the polymorphic nature of black yeast, Saccharomyces cerevisiae's cell morphology is relatively stable, which facilitates standardized control of the fermentation process.
The structural composition, synthesis, and regeneration of the Saccharomyces cerevisiae cell wall are closely related to the yeast's own reproduction and environmental stress. The cell wall is primarily composed of glucans, mannans, chitin, proteins, phosphates, and lipids. beta-glucan accounts for 30-35% of the cell wall dry weight and is the primary structural component.
Black yeast and Saccharomyces cerevisiae exhibit fundamental differences in their glucan production mechanisms.
The glucan produced by black yeast is an exopolysaccharide, produced by the bacteria itself outside the cell during fermentation. This unique production mechanism allows black yeast to produce beta-glucan through simple heat treatment, without the need for complex chemical extraction or purification.
The β-glucan produced by black yeast is primarily composed of beta-1,3- and beta-1,6-linked glucose units, resulting in a highly branched polysaccharide structure. Through specialized biotechnological cultivation methods, black yeast is able to continuously secrete β-glucan into the culture medium during fermentation, forming a highly concentrated polysaccharide solution.
The β-glucan produced by Saccharomyces cerevisiae is a structural component of the cell wall, present in the inner layer of the cell wall and constituting 30-35% of the cell wall dry weight. This glucan is produced through an intracellular biosynthetic pathway involving multiple enzymatic reactions.
Due to their different production mechanisms, the extraction processes for the two yeast glucans differ significantly. Since black yeast glucan is an extracellular polysaccharide, it can be obtained through simple filtration and concentration. In contrast, cerevisiae yeast glucan requires complex processes such as cell disruption and chemical extraction.
Black yeast glucan and Saccharomyces cerevisiae glucan share similarities in chemical composition and glycosidic bond types, but also exhibit significant differences.
β-glucan produced by black yeast is a highly branched polysaccharide. Its backbone is composed of β-1,3-D-glucan, with side chains consisting of β-1,6-glucose residues. The content of β-1,6-linked glucose residues exceeds 70%. This highly branched structure is a distinctive feature of black yeast glucan.
Saccharomyces cerevisiae β-glucan is primarily composed of β-1,3-D-glucan as the backbone and β-1,6-D-glucan as the side chains. It is a water-insoluble, branched polymer. Its main chain is linked by β-1,3 glycosidic bonds, and the side chains are linked by β-1,6 glycosidic bonds. This structural feature is similar to that of black yeast glucan, but there are differences in branching degree and specific structure.
Molecular weight is a key factor influencing the physicochemical properties and biological activity of glucans. Significant differences exist in the molecular weight distributions of black yeast glucans and Saccharomyces cerevisiae glucans.
Black yeast glucans typically have a high molecular weight. Gel chromatography analysis using pullulan as a standard and sodium hydroxide as a developing solvent shows that β-glucans produced from black yeast have molecular weights exceeding 1,000,000 Da. This high molecular weight is a key structural characteristic of black yeast glucans and is closely related to their high degree of branching and unique triple-helical structure.
Saccharomyces cerevisiae β-glucans have a wide molecular weight range, typically between 20 and 4,000 kDa, with a typical molecular weight of approximately 250,000 to 1,000,000 Da.
The two glucans differ significantly in their molecular configuration and spatial structure, particularly in their three-dimensional structure.
Black Yeast Glucan has a typical triple helical structure.
Saccharomyces cerevisiae β-glucan also has a triple helical structure, with molecular weights ranging from tens of thousands to hundreds of thousands, existing as a three-stranded helix. Research has shown that the structure of Saccharomyces cerevisiae β-glucan differs from the linear molecular structure of common sugars, exhibiting a unique triple ultrahelical structure.
Both black yeast glucan and Saccharomyces cerevisiae glucan exhibit significant immunomodulatory activity, but their mechanisms of action differ.
Black yeast glucan exhibits broad immunomodulatory functions, particularly in intestinal immunity. Studies have shown that β-1,3-1,6-glucan has multiple functions, including immunomodulatory effects, particularly in the intestine; anti-tumor and anti-metastatic effects; and can alleviate influenza and food allergies, as well as reduce stress.
The immunomodulatory mechanism of Saccharomyces cerevisiae β-glucan is primarily achieved through activation of the innate immune system. Studies have shown that Saccharomyces cerevisiae β-glucan can activate the Nrf2/HO-1 signaling pathway mediated by its receptor, Dectin-1. In an oxidative stress model, β-glucan significantly upregulates LPS-induced expression of Dectin-1, Nrf2, and HO-1, inhibiting ROS production. Saccharomyces cerevisiae β-glucan can also act through multiple receptors. In vivo experiments, Saccharomyces cerevisiae β-glucan can enhance the phagocytic function of macrophages.
Based on the above analysis, a comprehensive comparison of the technical performance of black yeast glucan and saccharomyces cerevisiae glucan is as follows:
Comparative Dimensions | Black Yeast Glucan | Saccharomyces cerevisiae glucan |
Source Characteristics | Exopolysaccharide, natural water-soluble | Cell wall components need to be extracted and purified |
Production Process | Simple, only heat treatment required | Complex, requiring cell disruption and chemical extraction |
Main Structure | β-1,3 main chain, β-1,6 branches (>70%) | β-1,3 backbone, β-1,6 branches (approximately 3%) |
Molecular Weight | >1,000,000 Da | 20-4000 kDa |
Immune Modulation | Outstanding intestinal immunity and good anti-allergic effect | Systemic immune activation and strong phagocytic function |