Bioprospecção de fungos de amostras de solo Amazônico com potencial para a produção de pigmentos

Abstract

Environmental isolates of filamentous fungi are widely studied for their ability to secrete metabolites of great commercial value, including pigments. These, in turn, find application to color textile raw materials, foods and medicines. In this context, the aim of this work was to select fungi from soil samples Amazon with potential for the production of pigments. For this, samples were collected from surface soil and colonies were isolated by serial dilution technique. The macro and microscopic characteristics of colonies grown within 72 hours were used for determining the gender of the isolates and the ITS region of the ribosomal DNA of fungal pigment producers was sequenced for identification to the species level. A cryopreservation technique and conservation at -70 C was employed to preserve the lines with biotechnological potential. A bioprocess performed in broth Czapeck enabled the selection of fungi which produce colored compounds. Fractions containing the pigments were extracted by use of solvents of different polarity and selection of the pigment of interest was due to the color intensity of the substance present in the fractions. The techniques used for the isolation and structural elucidation of the sample of interest involved chromatographic fractioning (Sephadex LH-20 column and microcrystalline cellulose column), recrystalization and NMR (Nuclear Magnetic Resonance). The influence of carbon sources and nitrogen on the yield of the isolated substance was also studied in this work. From samples collected was possible to isolate 50 soil fungi. Of these five strains were able to produce pigments during fermentation. Producing fungi were identified as Penicillium sclerotiorum 2AV2, Penicillium sclerotiorum 2AV6, Aspergillus calidoustus 4BV13, Penicillium citrinum 2AV18 e Penicillium purpurogenum 2BV41. Penicillium sclerotiorum 2AV2 produced fractions very colorful and was chosen to continue the activities of the chemical characterisation. After isolation of the substance was obtained as a yellow-orange powder, which was identified by NMR as sclerotiorin, a major metabolite that has not been previously described by synthesis by fungi from the Amazon. The influence of carbon and nitrogen sources for production of sclerotiorin was analised and it was found that rhamnose and peptone increased yield when used separately. These results indicate that Amazonian fungi bioprospecting is an alternative to search for new sources of natural dyes, since it allows to exploit the biotechnological potential of our region while allowing knowledge of species of microorganisms producers.