The present invention relates to a process for obtaining fermentable sugars from whole barley, involving treating hulled barley with H2SO4 to produce acid treated barley and treating the acid treated barley with enzymes to produce fermentable sugars.
Barley is currently being used for ethanol production in Europe. Barley has some advantages as a corn substitute for ethanol production outside the Corn Belt in the U.S., particularly on the East Coast, the upper Midwest, and the Northwest (U.S. Department of Agriculture-National Agricultural Statistics Service (USDA-NASS), 2006, Crop Acreage and Yield US Maps Showing Counties Crop Year 2005 United States, <http://www.nass.usda.gov/Charts_and_Maps/Crops_County/index.asp> (accessed April, 2008)). North America grows approximately 14% of the world annual production of barley (Kim, S., and B. E. Dale, Biomass & Bioenergy, 26(4): 361-375 (2004)). Most fuel ethanol in the U.S. is corn-based. Hence most production facilities are located in the Corn Belt and not on either of the coasts where demand for ethanol is high (Hsu, T. A., Pretreatment of biomass, In: Wyman, C. E. (Ed.), Handbook on Bioethanol: Production and Utilization, 1996, Taylor & Francis Inc, Bristol, Pa., pp. 179-212).
Agronomically, winter barley fits extremely well into a three-crop two-year rotation with corn and soybeans. Barley grows well in areas where corn does not, and so might become a financially cost-effective source of fermentable sugars (e.g., ethanol feedstock) for those regions (Welsh, J. P., et al., Developing Strategies for Spatially Variable Nitrogen Application in Cereals, Part 1: Winter Barley, Biosystems Engineering, Vol. 84(4), pages 481-494 (2003); USDA-NASS, 2006). However, there are major obstacles in the barley ethanol conversion process, including (1) difficulty of clean separation of hull (lignocellulose) from the endosperm which makes the downstream conversion process more complicated, (2) high viscosity of mash in the liquefaction step due to mixed linkage β-glucan polysaccharides, and (3) difficulty of the conversion of the lignocellulosic hull into ethanol. Thus there is a need for a new process for producing fermentable sugars from barley.