Upstream Parameters Affecting the Cell Growth and Xylitol Production by Candida guilliermondii FTI 20037

Abstract

The effects of yeast extract (0-10g/l), methanol (0-10%v/v), acetic acid (0-1.0g/l), furfural (0-0.5g/l), glucose (0-30g/l), inoculum age (15-70h) and product concentration (18-230g/l) on the xylose-xylitol conversion by Candida guilliermondii FTI 20037 were studied. The xylitol specific productivity increased about 35% at a yeast extract concentration of 1.0g/l, whereas glucose showed a strong inhibitory effect on the xylitol production and a stimulating effect on the growth of C. guilliermondii. Methanol, acetic acid and furfural under the employed concentrations did not show any positive effect neither on the growth or on the xylose-xylitol conversion by the yeast. The inoculum age showed a strong influence on xylitol formation and the best fermentative parameters were attained using a 40-h inoculum age. A xylitol concentration in the fermentation medium higher than 80g/l inhibited mark­edly the xylitol productivity by the yeast C. guilliermondii.

Sugarcane Bagasse-Based Ethanol Production and Utilization of Its Vinasse for Xylitol Production as an Approach in Integrated Biorefinery

“…Xylitol production from D-xylose by C. tropicalis DMS 7524 degenerated when 15 g/L of yeast extract were added to the media [33]; the study recommended adding no more than 1 g/L of yeast extract to the medium for xylitol production. A similar result was also obtained in C. guilliermondii FTI 20037, where adding yeast extract of more than 1 g/L resulted in decreasing xylitol concentration, although the cell growth improved [34]. A decreasing trend in xylitol production with increasing yeast extract was reported for C. tropicalis NRRLY-12968 growing in the acid hydrolysate of mung bean hull [35].…”

Semi-continuous xylitol bioproduction in sugarcane bagasse hydrolysate: effect of nutritional supplementation

“…Generally, very high concentrations of nutrients stimulate cell growth, while a minimal optimal supplementation favors FIGURE 2 -Specific rates of xylose consumption (a), xylitol production (b) and cell growth (c,d) throughout the repeatedbatch fermentations: , supplemented hydrolysate (Assay A); , non-supplemented hydrolysate (Assay F). xylitol production (Silva et al, 1994;Sirisansaneeyakul et al, 1995;Silva et al, 1997). Considering the results achieved in the present study, the supplementation of the SBHH with both ammonium sulfate and rice bran extract should be performed throughout all the repeated batches in order to improve the xylose-to-xylitol bioconversion.…”

Supplementation requirements of brewery’s spent grain hydrolysate for biomass and xylitol production by Debaryomyces hansenii CCMI 941

“…Therefore, it is important to identify both the type and the minimal supplement requirements to minimise the costs involved in media formulation for both the first and second steps of the xylitol bioprocess. Furthermore, in some cases, high concentrations of nutrients may favour cell growth to the detriment of xylitol production [40], which highlights the need for an accurate medium formulation. This knowledge is also important to further the progress towards xylitol industrial application by minimizing nutrient addition and simplifying the fermentation process design.…”