Metabolização da celobiose por leveduras isoladas a partir de biomassa lignocelulósica em decomposição

Abstract

The metabolization of cellobiose is one of the limiting factors for a successful production of second-generation ethanol; however, Saccharomyces cerevisiae, which continues to be the most well-adapted yeast to the alcoholic fermentation industry, is known to be unable to use this disaccharide. Tanking into account that, in local forests, as well as in any similar biome, lignocellulosic biomass is decomposed by microorganisms such as yeasts, which, unlike S. cerevisiae, can utilize cellobiose, this work aimed the isolation and characterization of yeast from the local microbiota, in order to select new strains which were able to efficiently metabolize this carbon source. We analyzed the profiles of cell growth and sugar consumption of 15 yeast strains, isolated from Conservation Unit of the National Forest Chapecó, from the campus of Universidade Federal da Fronteira Sul, from the park around the Grotto of Our Lady of Guadalupe and from Palmital Park – all of them, located in the City of Chapecó. Among the strains analyzed, 14 showed ability to metabolize cellobiose, although with different rates of sugar consumption. The periplasmic and intracellular activity of the enzyme cellobiase in 5 strains were also evaluated. The intracellular activity was in general higher than the periplasmic. The results also suggest that glucose inhibits the expression of cellobiase. Thus, the isolated strains showed interesting features for the ethanol industry. Further studies can now provide a parallel between the performance of these yeasts in industrial conditions and a heterologous expression of its celobiases in S. cerevisiae, in order to find the most efficient application.