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Abstract
Increasing chromosome number of Pachysolen tannophilus above the haploid level increased the yield of ethanol from d-xylose. There was a large increment on going from the haplophase to the diplophase, and the highest yields were obtained with either a triploid or a probable tetraploid, depending on the concentration of d-xylose. In addition, the rate of ethanol production from d-xylose and d-glucose increased, with the increment being larger on d-xylose. On d-galactose, the amount of ethanol produced within a given time also increased. The level of a by-product from d-xylose, xylitol, decreased on going from a haploid to higher ploidy, but there was no discernible trend for two other by-products, acetic acid and arabinitol. Increasing ploidy increased growth rate on d-galactose, but not appreciably on d-xylose. The altered properties on D-xylose of the strains tested were not due to increased levels of either d-xylose reductase or xylitol dehydrogenase, nor probably of alcohol dehydrogenase.
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