17-12: Simultaneous co-fermentation of mixed sugars: a promising strategy for producing cellulosic biofuels and chemicals

Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Suk Jin Ha1, Eun-Joong Oh2, Soo Rin Kim2, Qiaosi Wei2, Jonathan M. Galazka3, Jamie H. Cate3 and Yong-Su Jin2, (1)Energy Biosciences Institute, University of Illinois at Urbana-Champaign, Champaign, IL, (2)Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL, (3)Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA
While fermenting mixed sugars (glucose, xylose, and galactose) in hydrolyzates from terrestrial or marine biomass, naturally existing or engineered microorganisms preferentially ferment glucose over non-glucose sugars. This sequential utilization often results in lower overall yield and productivity of biofuels. To overcome these bottlenecks, we engineered yeasts to co-ferment mixtures of cellobiose and xylose. After constructing an efficient xylose-fermenting strain of Saccharomyces cerevisiae through rational and combinatorial strategies, we introduced a cellobiose utilizing pathway into the xylose-fermenting strain. In this yeast strain, hydrolysis of cellobiose takes place inside yeast cells through the action of an intracellular β-glucosidase following import by a cellodextrin transporter (1). The resulting yeast strain not only co-fermented cellobiose and xylose simultaneously, but also exhibited improved ethanol yield as compared when either cellobiose or xylose was used as a sole carbon source (2). With a similar strategy, we demonstrate that co-fermentation of cellobiose and galactose (3) and enhanced production of xylitol from a mixture of cellobiose and xylose (4) are also feasible. Our results suggest that this simultaneous co-fermentation of mixed sugars is a promising strategy for producing fuels and chemicals from plant biomass.
  1. Galazka et al. Science 330:84-86 (2010)
  2. Ha et al. Proc. Natl. Acad. Sci. USA 108:504-509 (2011) 
  3. Ha et al. Appl. Environ. Microbiol. 77: 5822-5826 (2011)
  4. Oh et al. AIChE Annual Meeting (2011)
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