Application of factorial design to the study of xylitol production from eucalyptus hemicellulosic hydrolysate

This study deals with the bioconversion of xylose into xylitol by Candida g uilliermondii FTI 20037 using eucalyptus hemicellulosic hydrolysate obtaine d by acid hydrolysis. The influence of various parameters (ammonium sulfate , rice bran, pH, and xylose concentration) on the production of xylitol was evaluated. The experiments were based on multivariate statistical concepts , with the application of factorial design techniques to identify the most important variables in the process. The levels of these variables were quan tified by the response surface methodology, which permitted the establishme nt of a significant mathematical model with a coefficient determination of R-2 = 0.92. The best results (xylitol = 10.0 g/L, yield factor 0.2 g/g, and productivity = 0.1 g/[L.h]) were attained with hydrolysate containing ammo nium sulfate (1.1 g/L), rice bran (5.0 g/L), and xylose (initial concentrat ion of 60.0 g/L), after 72 h of fermentation. The pH of fermentation was ad justed to 8.0 and the inoculum level utilized was 3 g/L.