Yeast Mannan: Structure, Extraction and Bioactivity

Background and Objective: Yeasts are cheap and easily available sources of valuable bioactive compounds such as mannan. Spend yeasts as byproducts of various industries can be used to extract mannan, making the production process economical. Various factors such as growth conditions and cultivation system affect cell wall structure of the yeasts. The most common use of yeast mannan is as a prebiotic in animal feed. Its metabolism in the intestinal cell wall can produce postbiotic compounds such as short-chain fatty acids. Extraction of mannan has not been reported as a known classical method, depending on its final use and costs. The most popular cost-effective method is the acid-alkaline strategy. The current article has reviewed all aspects of structure, methods of extraction and recent studies on potential uses and bioactivities of yeast mannan and mannooligosaccharides, including modulation of animal gut microbiome, immune system and animal performance, as well as its antioxidant activity. Results and Conclusion:  Literature review shows that mannan, manno-oligosaccharides, mannan rich fraction and their combination with probiotics and/or other bioactive compounds such as β-glucan may modulate compositions of gut microbiota. Various studies have shown that effectiveness of mannan depends on the species of animals and their age, diet, environmental conditions and rearing system. By optimizing the growth and cultivation conditions of yeasts, it is possible to increase proportions of mannan in the cell wall of yeasts, increasing efficiency of the industrial production. Although the most widely used yeast in industries is Saccharomyces cerevisiae, other Saccharomyces strains (e.g., Saccharomycesboulardii) and non-Saccharomyces yeasts (e.g., Pichia and Kluyveromyces spp.) can also be considered as high yielding strains.