Hung Lee

Screening of yeasts for production of xylitol fromd-xylose and some factors which affect xylitol yield inCandida guilliermondii

SummaryThe ability to convertd-xylose to xylitol was screened in 44 yeasts from five genera. All but two of the strains produced some xylitol with varying rates and yields. The best xylitol producers were localized largely in the speciesCandida guilliermondii andC. tropicalis. Factors affecting xylitol production by a selectedC. guilliermondii strain, FTI-20037, were investigated. The results showed that xylitol yield by this strain was affected by the nitrogen source. Yield was highest at 30–35°C, and could be increased with decreasing aeration rate. Using high cell density and a defined medium under aerobic conditions, xylitol yield byC. guilliermondii FTI-20037 from 104 g/ld-xylose was found to be 77.2 g/l. This represented a yield of 81% of the theoretical value, which was computed to be 0.9 mol xylitol per mold-xylose.

Correlation between limitation of growth ofPachysolentannophilus on D-xylose with the formation of ethanol and other products

The formation of ethanol, xylitol, ribitol, arabitol and acetic acid from D-xylose byPachysolentannophilus correlated with the limitation of growth. The correlation was consistent with these products being secondary metabolites.

Ethanol production from xylitol and some other polyols byPichiaangophorae

Several strains of the yeastPichiaangophorae produced ethanol from xylitol in yields that were as high as 0.3 g ethanol/g xylitol used. One of the strains also produced ethanol from D-sorbitol and D-mannitol. The ability to produce ethanol from xylitol and sorbitol is of interest in efforts to increase the yield of ethanol in fermentations where these two polyols are produced as by-products.