Selection and identification of xylose-fermenting yeast strains for ethanol production

Abstract

Ethanol production from lignocellulosic biomass is interesting to the economy due to the pressure to reduce the consumption of fossil fuels and the use of lands for non-edible crops. Xylose is one of the main sugars obtained by hydrolysis of hemicellulose fraction of biomass; however, industrial yeasts cannot ferment it. This work aimed to select, characterize and identify xylosefermenting yeasts from a collection of Brazilian microorganisms with potential use in ethanol production. Xylose assimilation was tested by replica plating, and fermentation was tested with Durham tubes. Xylose-fermenting strains had their fermentative capacity quantified and compared to a reference strain (Scheffersomyces stipitis UFMG-IMH 43.2) and were identified by molecular techniques. Three strains isolated from plant exudates were able to ferment xylose and showed fermentative parameters similar to the reference strain. Two strains were additionally identified as Candida parapsilosis and one was identified as Meyerozyma guilliermondii. The findings show the potential biotechnological use of these microorganisms.