Mushrooms Pleurotus spp. group are known to be the highly efficient species in lignin degradation. They are distributed worldwide forests in temperate climates. A study of their extracellular polysaccharides and mycelial polysaccharides from this group is of interest since they might have great potential application on medicine. Pleurotus eryngii is one of the edible mushrooms currently popular as food and medicine. Now, in order to obtain extracellular polysaccharides, the basidiomicete Pleurotus eryngii was isolated and cultivated in submerged culture. Fruiting body fragments were isolated from a PDA solid medium, incubated at 25ºC, shaken. Submerged cultures (medium POL) grew at 25 ºC for 10 days. The mycelia were then removed by centrifugation (yield: 5.14 g/L of culture medium). The liquid medium was treated with ethanol (3:1, v/v) and the precipitate dialyzed against tap water, and freeze-dried to obtain extracellular polysaccharides (EPS, yield: 241 mg/L of culture medium). EPS (2.9 g) was treated with water at 100ºC for 3 h. The water-soluble polysaccharides (1.39 g) were isolated and submitted to freeze-thawing, resulting in a soluble (fraction A) and water-insoluble (fraction B) material. Fraction A (574 mg) was treated with Fehling solution, which gave an insoluble Cu²⁺ complex, consisting of a pure mannan (fraction A1, 275 mg). Its ¹³C NMR, when compared with literature ¹³C shifts (Gorin, P. A. J., Can. J. Chem., 51:2375-2383, 1973), suggest a structure with a main chain of (1→6)-linked α-D-Manp residues, near all of them being substituted at O-2 with side chains of different lengths, and which contained 2-O- and 3-O-substituted α-Manp units. Fraction B had glucose as its main monosaccharide and in accordance to ¹³C NMR data, this it had a similar structure as described for the fruiting body of P. eryngii (Carbonero, E. R., et al. Carbohydr. Polym., 2006, in press) It was a branched b-glucan, scleroglucan, with a main chain of (1®3)-linked-Glcp residues, substituted at O-6 by single-unit b-Glcp side chains. Additional studies are being carried out in order to determine the fine chemical structure of these fractions.

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