Extração e caracterização química de polissacarídeos de basidiomicetos comestíveis de ocorrência na Amazônia

Abstract

Besides being useful for human consumption, fungi are versatile organisms that degrade organic matter, producing value added substance. Among the bioactive substances present in these fungi, polysaccharides are the main products, which have a high value for chemical, pharmaceutical and medical industries. Knowing that the Amazon presents the greatest biodiversity of the planet and that in this forest there is still little information about the species of native basidiomycetes, the objective of the study was the cultivation of edible mushrooms Lentinus strigosus and Pleurotus ostreatus in regional wood residues as a substrates, aiming the extraction and Chemical characterization of polysaccharides isolated from the fruiting body of these mushrooms. For the cultivation, regional wood residues were used, according to the following substrate formulation: 68% sawdust of Simaboura amara (marupá) or Anacardium giganteum (cajuí), cereal meal mixture (30%) and calcium carbonate (2 %), homogenized and humidified to 75%. The substrates were autoclaved, inoculated and kept in a climatic chamber until complete colonization, and then transferred to the production chamber. After the fruiting, the mushrooms were harvested, dehydrated and analyzed for yield. They were grounded and successively subjected to cold and hot water extractions for subsequent purification and characterization of polysaccharides. The fractions obtained containing polysaccharides were purified by the process of freezing and thawing, Fehling solution and dialysis membranes with 12-14 kDa exclusion limit. The chemical structure of the polysaccharide was determined by an analysis of the monosaccharide composition, NMR and methylation. Regarding to the production, the results showed that the formulation containing cajuí allowed better results of biological efficiency (EB 221,17 and 104,88%); Yield (220.23 g kg-1 and 72.5 g kg-1) for P. ostreatus and L. strigosus, respectively. The organic matter loss (OML) was not significantly different for the two types of substrates used. Three β-D-glucans were isolated from the hot extraction (IHW-fraction A, B and C), which contains the main chain composed of β-D-Glcp units connection (1→ 3), and may be replaced by O-6 for β-Glcp terminals. Besides, these were isolated homopolysaccharide (methylated galactan) of cold extraction. Thus, it is possible to use regional waste timbers for the cultivation of native edible fungi in the Amazon region. The glucans described in this study are similar to those that have biological effects reported in scientific literature, as it is likely that they have a therapeutic potential.