Production of ethanol and xylitol from D-xylose by four strains of Candida (Spathaspora) materiae

Abstract

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.

Keywords

• Candida materiae
• cell concentration
• ethanol
• oxygen-limiting condition
• sugarcane bagasse hemicellulose hydrolyzate
• xylitol