Abstract Xylose is the most abundant pentose sugar in lignocellulosic biomass and can be biologically converted into economically important products by microorganisms such as yeasts. This study aimed to characterize the bioconversion of xylose into xylitol and ethanol using four strains of Candida materiae belonging to the Spathaspora clade, which includes yeast species with the potential to convert D-xylose to xylitol and ethanol. Fermentation assays were performed in YPX medium (yeast extract, peptone, xylose 5%) under two oxygen-limiting conditions at inoculum concentrations of 1, 5 and 10 g L-1. The best results were obtained using a 5 g L-1 inoculum under moderate oxygen-limiting conditions. C. materiae UFMG-CM-Y480 produced 32.23 g L-1 of xylitol, yielding 0.743 g g-1 within 36 h. Different combinations of xylose and glucose (25/25 g L-1, 40/10 g L-1, 10/40 g L-1) were also used to verify the influence of sugars on C. materiae metabolism. Xylitol was preferentially produced in medium containing 40 g L-1 xylose. C. materiae UFMG-CM-Y480 produced 26.20 g L-1 of xylitol with a yield of 0.646 g g-1 in 36 h. Our results showed that C. materiae UFMG-CM-Y480 may convert D-xylose to xylitol with a better fermentative performance than other xylitol-producing yeasts.

ABSTRACT There is an increase in researches to create alternative fuels through the use of biomass and agroindustrial lignocellulosic residues. The present study proposes the use of rice bran as source of energy with the potential to enhance bioethanol production. Using different concentrations of cells (1-5 g.L–1) and rice bran (2.5-7.5 g.L –1) with Saccharomyces cerevisiae, a factorial design 22 was carried out. The nutrient source provided by rice bran affects the substrate conversion in product (Yp/s) response in a quadratic form, but its linear form showed no significant effect (α = 0.05). When it comes to means, the best results were obtained for 12 h and for fermentation medium 2 (23.320 g.L–1 of ethanol), which contained the highest rice bran concentration and the lowest initial cell concentration. Medium 3, consisting of 2.5 g.L–1 and 5 g.L –1 of rice bran and cells, respectively, showed the lowest K s (4.434 g.L–1).