J. Microbiol. Biotechnol. (2009), 19(5), 455–461 doi: 10.4014/jmb.0809.542 First published online 24 February 2009 Structural Characteristics of Immunostimulating Polysaccharides from Lentinus edodes Lee, Hee Hwan 1 , Jong Seok Lee 1 , Jae Youl Cho 2 ,Young Eon Kim 3 , and Eock Kee Hong 1 * Department of Bioengineering and Technology, Kangwon National University, Chuncheon 200-701, Korea School of Bioscience and Biotechnology, and Institute of Bioscience and Biotechnology, Kangwon National University, Chuncheon 200-701, Korea Korea Food Research Institute, Sungnam 463-746, Korea Received: September 22, 2008 / Revised: October 21, 2008 / Accepted: October 27, 2008 There is a significant amount of experimental evidence suggesting that polysaccharides from mushrooms enhance the host immune system by activating various mechanisms in immune cells, including macrophages. In this study, polysaccharides from Lentinus edodes were found to stimulate the functional activation of macrophages to secrete inflammatory mediators and cytokines and increase the phagocytotic uptake. The chemical properties of the stimulatory polysaccharides, CPFN-G-I, CPBN-G, and CPBA-G, were determined based on their monosaccharide composition, which mainly consisted of glucose and mannose. According to FT - IR and GC/MS, the structure of CPFN- G-I, purified from the fruiting body of L. edodes, was found to consist of a β-1,6-branched-β-1,4-glucan, whereas CPBN-G and CPBA-G, purified from the liquid culture broth, were found to be composed of a heteromannan. The configuration of the β-linkage and triple helical conformation of each polysaccharide were confirmed using a Fungi-Fluor kit and Congo red, respectively. Keywords: Lentinus edodes , immunostimulating polysaccharide, mushroom-derived β-glucan, triple helical conformation, Congo red, structural analysis A number of bioactive molecules, including antitumor agents, have recently been identified in various higher basidiomycete mushrooms. Furthermore, since the polysaccharides of these mushrooms are known to have no toxic side effects, unlike existing anticancer chemical medications, when used as a cancer therapeutic, these polysaccharides are able to prolong the life span of cancer patients [1]. Thus, polysaccharides are the best known and most potent mushroom-derived substances displaying immunomodulating properties [15, 22]. Pharmacological studies are currently being conducted on the antitumor activity of the polysaccharide β-1,6-branched-β-1,3-glucan from hot-water extractions of L. edodes, as it was shown to display antitumor activity against Sarcoma 180 in the 1970s [10, 33]. In most cases, the antitumor activity of polysaccharides is exerted by activating the immune responses of the host organism, such as complementary system activation [12], macrophage- dependent immune system responses [17, 23], and upregulation of interferon expression [8]. Polysaccharides have also been reported to decrease asthenia symptoms, such as fever, which is caused by the tumor necrosis factor (TNF) and anemia [5]. The immunomodulating activities of polysaccharides are usually characterized according to their chemical composition, molecular weight, conformation, glycosidic linkage, and degree of branching. [7, 21, 34]. Biologically active polysaccharides are widespread among mushrooms, and most have unique structures in different species. As a result, several studies have already been conducted to determine the precise structures of these different polysaccharides. Accordingly, the primary goal of this study was to determine the immunostimulating activities and structural characteristics of the following polysaccharides from Lentinus edodes: the neutral fraction from the fruiting body (CPFN-G-I, 580 kDa), the neutral fraction from the cultured cell-free broth (CPBN-G, 40 kDa), and the acidic fraction from the cultured cell-free broth (CPBA-G, 46 kDa). MATERIALS AND METHODS Materials The strain used in this study was Lentinus edodes KCTC 6734, which was grown in a liquid containing 60 g/l glucose, 10 g/l yeast *Corresponding author Phone: +82-33-250-6275; Fax: +82-33-243-6350; E-mail: ekhong@kangwon.ac.kr