(558d) Selective Fermentation of Six Carbons Sugars from Hot-Water Hardwood Extract Hydrolysates

Liu, S., SUNY College of Environmental Science and Forestry
Hot water wood extract hydrolysate contains a mixture of sugars: xylose, glucose, galactose, mannose, arabinose and rhamnose. This sugar mixture presents a challenge in fermentation to ethanol and other chemicals / biofuel. The fermentation efficiency is especially low for xylose. When genetically modified E. coli fbr5 was employed to ferment the sugar mixture to ethanol, glucose was the first sugar consumed, and then galactose, arabinose, mannose and rhamnose, xylose was the last to be consumed. While E. coli fbr 5 was genetically engineered to ferment Xylose, this outcome is disappointing. Most microorganisms prefer glucose, E coli is no exception. Xylose being the dominant sugar species in hardwood hot-water extract hydrolysate and the least preferred sugar for ethanol production present a challenge to the biomass energy industry development. On the other hand, xylose can be employed to produce xylitol, furfural, and a lot more products efficiently. The value of xylose is higher than glucose in the market, and yet it is limiting the efficiency in biomass conversion. Hot water wood extract hydrolysate was subject to fermentation with S. cerevisiae and xylose was left unconsumed. Xylose can be recovered from the fermentation broth, while ethanol was produced from glucose.