Hidrólise de xilana e metabolização de xilose por leveduras isoladas da biomassa lignocelulósica em decomposição

Abstract

Hydrolysis of lignocellulosic compounds, such as xylan, and xylose metabolism, the main product of this hydrolysis, are limiting factors for the production of second generation ethanol. In order to better understand these two steps, the present study aimed to isolate and to characterize yeasts belonging to the local microbiota. We analyzed 16 strains, which were isolated at Universidade Federal da Fronteira Sul, Conservation Unit of the National Forest Chapecó, Nossa Senhora de Guadalupe Grotto Park and Palmital Park, located in the city of Chapecó. Among the analyzed strains, 14 of them were able to grow on media with glucose, 13 were able to grow on xylose and 3 on xylan. The glucose was the fastest carbon source to be consumed by the cells. The xylanase activities, induced by xylan or xylose, were also analyzed. Our results demonstrated that the enzyme activity in cells grown on xylan is higher than in cells grown on xylose, suggesting that xylose does not induce the enzymatic activity and can act as a repressor of this enzyme expression. Furthermore, our data also suggest that the activity of xylanases is higher in the final stages of cell growth, indicating that the products of enzymatic hydrolysis are more powerful inducers of the gene expression. The present study also enabled us to identify strains which can contribute to the optimization of the second generation ethanol production.