Resumo

Sugarcane is the main source of first generation ethanol, whereas Brazil is the main sugarcane producer, generating tons of sugarcane bagasse and straw every year. Hydrolysis of this lignocellulosic biomass and its fermentation would allow duplicate ethanol production, however, the cost of hydrolytic enzymes and low yield of pentose fermentations constitute major limitations. Thus, it is important to improve enzyme production and the fermentations, whereas one of the possibilities is to select more adapted strains for the processes. This work aimed to isolate microorganisms naturally occurring in the sugarcane bagasse and to determine the number of filamentous fungi, yeast and bacerial isolates. Samples of 5 g of bagasse were transferred to sterile Erlenmeyer flasks and homogenized with sterile distilled water. Aliquots of 50 µl were collected from the filtrates and spread onto agar slants of potato dextrose (PDA), Vogel minimal medium (MMV), Czapek, Sabouraud (SB), Luria-Bertoni (LB). Cultures (triplicate) were incubated at room temperature and 30°C for 7 days. After growth and isolation, macroscopic and microscopic morphologies were observed to characterize filamentous fungi, yeast and bacterial strains. Fungal strains were transferred to MMV; yeast and bacterial strains were transferred to SB and LB tubes. It was observed that cultures incubated at 30°C presented greater variety of microorganisms. It were isolated 74 filamentous fungi, 8 yeasts and 147 bacterial strains. Filamentous fungi were mainly isolated in MMV (34), PDA (26) and Czapek (13). Only one filamentous fungus was isolated from SB. Yeasts were isolated from SB (3), LB (2), Czapek (2) and MMV (1). Most of bacteria grew in LB (45) and SB (41), followed by PDA (22), MMV (22) and Czapek (17). Isolates showed great diversity of morphology, what is positive for a further trial of enzyme production and pentose/hexose fermentations. Although the number of filamentous strains isolated was satisfactory for a trial, the number of yeasts was low and is not enough for a wide trial of new fermenting strains. These data allow to conclude that more samples should be analyzed and a treatment is necessary to increase the number of yeasts. The work opened the perspective of evaluating new filamentous fungi isolates for cellulase, xylanase and phenol-oxidase production on sugarcane residues.