Ethanol Fermentation From Lignocellulose

Using fuel ethanol as a substitute for gasoline, is expected to be a hotspot at present because of the diminishing of crude oil and natural gas resource, and the concerns related to economic stability, environmental impact and global warming. Cheap raw material and high ethanol yield are needed for commercial fuel-ethanol production . Xylose accounts for up to 30% of lignocellulose sugars, so effective xylose fermentation is one of the most critical features in the industrial ethanol production from lignocellulose. In order to get some high - yield strains, the main research contents of our task are optimization of ferment condition, carring on UV and chemistry mutagen to Pachysolen tannophilus, different mutant modes and screening factors were used.The fermentation property of the wild yeast 1125-3, which can quickly and effectively ferment xylose to ethanol, was studied. After domestication and cultivation, the utilization ratio of xylose is 92.92%, the ethanol yield rate is 12.88%. Effects of culture condition, including temperature, pH value and nitrogen source on fermentation were investigated. The optimum temperature and pH value of the growth were 30℃and 4.6～5.0, respectively. The optimum temperature and pH value of the xylose fermentation were 37℃and 4.6～5.0, respectively. The growth and fermentation were good with urea as the nitrogen source. When a mixed sugar with 2.5% glucose and 2.5% xylose was present in the fermentation culture medium, the ethanol yield rate of strain 1125-3 can attain the pure glucose fermentation level.Pachysolen tannophilus was taken as the the starting strain and the ethanol yield rate as screening factor, after UV and chemistry mutagen, a stable strain Z30-4 was obtained. After 72h of fermentation at 30°C and an agitation rate of 100rmp on a rotary shaker, the alcohol concentration is 13.33g·L^-1 and the ethanol yield rate is 81.15%, which was increased by 200% compared with original strain. The utilization ratio of xylose is 71.42 %, as same as the original strain.The fermentation quality of Pachysolen tannophilus degenerated during breeding. The degenerated strain was purified and rejuvenated by adjusting the kind of nitrogen source and the c/n. The fermentation cycle was shorten after rejuvenation. After 48h of fermentation, the ethanol fermentation power of the rejuvenated strains were about 150% of the original retrogressive strains.