Lipid-enhanced ethanol production from xylose by Pachysolen tannophilus
A number of different yeasts are now recognized as being capable of fermenting the pentose sugar, D-xylose, into ethanol. The most prominent among these are Pachysolen tannophilus and several Candida species. D-Xylose is found principally in lignocellulosic materials where it occurs as the main constitutent of the hemicellulosic xylans (1,4-..beta..-D-heteroxylans). With the exception of Candida XF-217, the conversion yields of xylose into ethanol for most yeasts were generally low (less than 70% of theoretical when grown on at least 50 g/l xylose). The low ethanol yields are attributable to a number of factors: 1) fermentation was not performed under conditions that maximize ethanol formation; 2) ethanol was not the major fermentation end-product, (e.g., acetic acid xylitol, and arabinitol are also known products, 3) ethanol toxicity; 4) ethanol is assimilated when the substrate becomes limiting; 4.8 and 5) osmotic sensitivity to high substrate levels, i.e. substrate inhibition. Attempts to increase ethanol yields of yeasts by adding exogenous lipids (e.g., oleic and linoleic acids, or ergosterol or its ester, lipid mixtures, or protein-lipid mixtures) to nutrient medium have succeeded in improving ethanol yields and also in reducing fermentation times. These lipids, when added to the nutrient medium, were incorporated into the yeast's cellular membrane. The protective action of these lipids was to alleviate the inhibitory effect of ethanol which then allowed the cells to tolerate higher ethanol levels. This communication reports on improved ethanol yields arising from the fermentation of xylose by a Pachysolen tannophilus strain when grown semi-aerobically in the presence of exogenous-added lipids. 17 references.
- Research Organization:
- CSIRO, Victoria, Australia
- OSTI ID:
- 5367398
- Journal Information:
- Biotechnol. Bioeng. Symp.; (United States), Vol. 28:4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
BIOREACTORS
ADDITIVES
ETHANOL
BIOSYNTHESIS
XYLOSE
FERMENTATION
BIOCHEMICAL REACTION KINETICS
BIOCONVERSION
CANDIDA
CELLULOSE
ECONOMICS
INHIBITION
LIGNIN
LIPIDS
SUBSTRATES
TOXICITY
YEASTS
ALCOHOLS
ALDEHYDES
CARBOHYDRATES
FUNGI
HYDROXY COMPOUNDS
KINETICS
MICROORGANISMS
MONOSACCHARIDES
ORGANIC COMPOUNDS
PENTOSES
PLANTS
POLYSACCHARIDES
REACTION KINETICS
SACCHARIDES
SYNTHESIS
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