Xylose fermentation to ethanol by new Galactomyces geotrichum and Candida akabanensis strains

Abstract

The conversion of pentoses into ethanol remains a challenge and could increase the supply of second-generation biofuels. This study sought to isolate naturally occurring yeasts from plant biomass and determine their capabilities for transforming xylose into ethanol. Three yeast strains with the ability to ferment xylose were isolated from pepper, tomato and sugarcane bagasse. The strains selected were characterized by morphological and auxanographic assays, and they were identified by homology analysis of 5.8 S and 26 S ribosomal RNA gene sequences. The identities of two lineages of microrganism were associated with Galactomyces geotrichum, and the other was associated with Candida akabanensis. Fermentative processes were conducted with liquid media containing only xylose as the carbon source. YP/S values for the production of ethanol ranging between 0.29 and 0.35 g g-1 were observed under non-optimized conditions.