UPSTREAM PARAMETERS AFFECTING THE CELL-GROWTH AND XYLITOL PRODUCTION BY CANDIDA-GUILLIERMONDII FTI-20037

The effects of yeast extract (0-10 g/l), methanol (0-10% v/v), acetic acid (0-1.0 g/l), furfural (0-0.5 g/l), glucose (0-30 g/l), inoculum a ge (15-70 h) and product concentration (18-230 g/l) on the xylose-xyli tol conversion by Candida guilliermondii FTI 20037 were studied. The x ylitol specific productivity increased about 35% at a yeast extract co ncentration of 1.0 g/l, whereas glucose showed a strong inhibitory eff ect on the xylitol production and a stimulating effect on the growth o f C. guilliermondii. Methanol, acetic acid and furfural under the empl oyed concentrations did not show any positive effect neither on the gr owth or on the xylose-xylitol conversion by the yeast. The inoculum ag e showed a strong influence on xylitol formation and the best fermenta tive parameters were attained using a 40-h inoculum age. A xylitol con centration in the fermentation medium higher than 80 g/l inhibited mar kedly the xylitol productivity by the yeast C. guilliermondii.