Isolamento e bioprospecção de cepas fúngicas do sudoeste do Paraná

Abstract

Polysaccharides from living organisms have different structures in relation to the monomeric composition, degree of branching, types of bonds and length of the chains. Exopolysaccharides (EPS) or extracellular polysaccharides, are biopolymers produced and excreted out of cells by some microorganisms. Many EPS can act as antioxidants, hypocholesterolemics, antivirals, bioremediation agents, among other functions. In submerged cultures, the exopolysaccharides can be recovered from the cell-free culture medium by simple processes such as dehydration with ethanol. The present work aimed the isolation of filamentous fungi and bioprospection as the production of EPS. Twenty strains of filamentous fungi were isolated from the rural region of Pato Branco and from the campus of the Federal Technological University of Paraná on Sabouraud-chloramphenicol agar plates. The fungi selected as producers of EPS were evaluated for the kinetic profile of EPS production and cell growth. The kinetic assays were conducted in 250 mL Erlenmeyer flasks, containing Minimal Vogel Medium, 20 g L-1 glucose, initial pH 5.5 in orbital incubator for 96h at 28 °C and 150 rpm. The exopolysaccharides produced were subjected to partial characterization by analysis of Infra-Red (IV-FT/ATR), X-Ray diffraction (XRD), scanning electron microscopy (SEM) and water solubility. Two strains of filamentous fungi were identified as promising EPS producers. The isolate no. 6 produced 1.31 g L-1 of EPS and 4.63 L-1 of mycelial biomass, while isolate no. 14 yielded 1.06 g L-1 and 2.64 g L-1 EPS and mycelial biomass, respectively. The infrared spectra of both EPS showed characteristic bands of polysaccharides, presence of glucose ring and suggest the presence of β type glycosidic binding. The X-Ray diffractograms showed that the EPS are predominantly amorphous, with semicrystalline regions. Scanning electron microscopy showed the presence of fibrillar structures and translucent thin films with irregular surface in both samples Particulate structures with irregular dimensions distributed along the surface were also observed in sample no. 14. Sample no. 6 showed higher solubility (47.08 mg 100 mL-1) than sample no 14 (35.42 mg 100 mL-1).