Process Alternatives for the Fermentation of Glucose/Xylose Mixtures by 'Pichiastipitis'

摘要

Technical substrates for the fermentative production of ethanol often containhexose and pentose sugars. For an optimal ethanol yield a complete conversion of all sugars in such a substrate is desired. Pichia stipitis, a yeast that can convert hexose as well as pentose sugars, shows the sequential use of substrate. Therefore pentose will not be converted when the hexose concentration is too high. A complete conversion to ethanol of a mixed substrate in a 'normal' continuous culture will be difficult. Furthermore P. stipitis needs oxygen for growth. However too much oxygen will shift the metabolism from ethanol to biomass production. The aim of the project was to find ways to convert a mixed substrate, which contains hexose and pentose sugars, using P. stipitis to ethanol in a continuous process with a high ethanol yield and production rate. For this purpose a model substrate that contained glucose (40 g/l;) and xylose (10 g/l) was used.