| dc.description.abstract | The use of lignocellulosic residues has been viewed as a reasonable alternative for energy and chemicals generation because of the wide availability of these materials. In the biorefinery, lignocellulosic biomass can be used as feedstock for the generation of different commercial value added products such as xylitol and second generation ethanol. The aims of this study were to isolate, identify and select yeast capable to ferment D -xylose for the possible use of these microorganisms in processes for the production of xylitol from hemicellulosic hydrolysate. Four hundred and fifty yeasts were obtained from 100 samples of sugarcane bagasse and 60 pie filters samples collected in the alcohol plants in Minas Gerais, São Paulo and Paraíba states. Twenty-four known yeast species were isolated, and three possible new species. Candida tropicalis was the most frequently isolated species. Candida tropicalis was the most frequently isolated species, followed by Trichosporon mycotoxinivorans and Candida tartarivorans. Nine other genera were obtained, represented by species usually found in plant materials. Of the isolates, strains of C. tropicalis, Lindnera bimundalis, Sugiyamaella smithiae and Zygoascus meyerae showed production of xylitol from D-xylose fermentation in test tubes with 2 ml of medium. In xylose fermentation assays on bench scale, these isolates produced xylitol the main product of fermentation. In tests of hemicellulosic hydrolyzate fermentation of sugarcane bagasse into flasks containing 100 ml of medium in a bench scale, L. bimundalis UFMG it BX21 produced high concentrations of xylitol. However, in the assay hydrolyzate fermentation in a bioreactor containing 1.5 liters of medium, this strain did not reproduce these resulatados although the production of xylitol has been checked in one of two test conditions employed where oxygen transfer rate was higher. The results of this work show the biotechnological potential of microorganisms isolated from waste like bagasse. The use of these microorganisms in the conversion of xylose to xylitol by the fermentation of hemicellulose hydrolysates derived from plant biomass can be possible by optimization of fermentation conditions in future studies. | |
