Aloke Bera1, Miroslav Sedlak2, Aftab Khan1, and Nancy Ho3. (1) Laboratory of Renewable Resources Engineering, Purdue University, 500 Central Dr., West Lafayette, IN 47907, (2) Laboratory of Renewable Resources Engineering/Department of Agricultural and Biological Engineering, Purdue University, 500 Central Dr., West Lafayette, IN 47907, (3) Laboratory of Renewable Resources Engineering/Department of Chemical Engineering, Purdue University, 500 Central Dr., West Lafayette, IN 47907
For the development of renewable fuel to solve the world’s energy problem, bioethanol represents the major renewable fuel for transportation. It can solve the transportation problem and also is a fuel better for the environment. Currently, most bioethanol is generated from starch or sugar, which is in limited supply. Cellulosic biomass, abundant available and renewable, is a promising alternative resource for bioethanol. The hydrolysates of cellulosic biomass contain large amounts of hexoses and pentoses, including glucose, galactose, mannose, D-xylose and L-arabinose.A lack of natural microorganisms that can convert all hexoses and pentoses to ethanol has been a major constraint. Most industrial ethanol fermentations now use the natural yeast Saccharomyces cerevisiae to rapidly and efficiently convert hexoses from starch and sugar to ethanol. However, the yeast is unable to ferment the pentose sugars (xylose and arabinose). Our laboratory altered the genetic structure of S. cerevisiae by cloning and overexpressing xylose reductase, xylitol dehydrogenase and xylulokinase, which make it possible to convert glucose and xylose to ethanol.The focus of this work is to establish an arabinose fermentation pathway in our glucose/xylose co-fermenting yeast S. cerevisiae 424A(LNH-ST). We have cloned and overexpressed genes encoding L-arabinitol 4-dehydrogenase and L-xylulose reductase in 424A(LNH-ST). The newly constructed strain can grow on arabinose and ferment arabinose present in cellulosic biomass to ethanol. Our new strain is also capable of co-fermenting a mixture of all sugars (glucose, mannose, galactose, xylose and arabinose) present in hydrolysates from any types of cellulosic biomass to the ethanol.
