Separation of Water-Soluble Polysaccharides and Melanin from an Extract of Wood-Destroying Fungi

Water-soluble and alkali-soluble polysaccharides have been isolated from the basidiomycete fungus Ganoderma lucidum (class Basidiomycetes). It has been established that the obtained aqueous and alkaline fractions mainly consist of glucan polysaccharides and melanins and are represented by a melanin–glucan complex. Methods have been developed for separating and purifying the melanin–glucan complex to a separate fraction of melanins and beta-glucans. The physicochemical properties of the obtained samples have been studied, and the purity of the obtained melanin and polysaccharide fractions has been established using UV spectroscopy. Based on the results obtained, it has been shown that melanin in the polysaccharide fraction made up ≤10%. The composition and molecular structure of the obtained melanin and polysaccharide samples have been established using gas chromatography and IR spectroscopy. The polysaccharide fractions mainly consisted of glucose residues (88–90.6%), and also up to 20.5% of fructose, xylose, and mannose residues as minor monosaccharides. The results of the study showed that the average molecular weight of the obtained polysaccharides and melanin ranged from 10 300 to 17 700 Da. The molecular weight distribution of polysaccharides obtained from the aqueous and alkaline fractions was 1.2, while that of melanin from the aqueous fraction was 1.1 and that of the alkaline fraction was 1.8.