FERMENTATION OF HEXOSES AND PENTOSES FROM HYDROLYZED SOYBEAN HULL INTO ETHANOL AND XYLITOL BY Candida guilliermondii BL 13

This work investigated the ability of a recently isolated strain of Candida guilliermondii to convert hexoses and pentoses obtained from acid-enzymatic soybean hull hydrolysates into ethanol and, in smaller amounts, into xylitol. Operational conditions and media formulation were optimized concerning ethanol production using experimental designs (Plackett-Burman and Central Composite Design). Results showed that C. guilliermondii BL 13 was capable of growing in non-supplemented, non-detoxified biomass hydrolysates, and the best culture conditions were determined to be 28 degrees C, pH 5.0, and 10(9) CFU mL(-1) of inoculum size. Ethanol productivity reached 1.4 g L-1 h(-1), and maximal yields of 0.41 g g(-1) were obtained, representing 80.4 % of the expected theoretical yields, whereas small amounts of xylitol were also produced. These results suggest that C. guilliermondii BL13 is a potentially useful yeast strain to be applied in second-generation ethanol production from lignocellulosic biomass based on its natural capacity to metabolize C-5 and C-6 sugars.