Metabolic Path to Improved Biofuel Production

(EurekAlert!/US Department of Energy Lawrence Berkeley National Laboratory) Researchers with the Energy Biosciences Institute (EBI), a partnership that includes the Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley, have found a way to increase the production of fuels and other chemicals from biomass fermented by yeast. By introducing new metabolic pathways into the yeast, they enable the microbes to efficiently ferment cellulose and hemicellulose, the two major families of sugar found in the plant cell wall, without the need of environmentally harsh pre-treatments or expensive enzyme cocktails.

"We've discovered new chemicals generated by fungi and bacteria as metabolites in their strategy for consuming the plant cell wall that are a general part of the global carbon cycle," says Jamie Cate, a staff scientist in Berkeley Lab's Physical Biosciences Division and a professor of biochemistry, biophysics and structural biology at UC Berkeley. "We should now be able engineer biofuel-producing yeast to do what these fungi and bacteria do, opening up many new possible scenarios for making biofuels and other important products."

Working through the EBI, Cate and a team of collaborators identified metabolic pathways in the fungus Neurospora crassa that are used to digest xylose, one of the most abundant sugars in hemicellulose. Yeast, Saccharomyces cerevisiae, the microbe most commonly used for the production of biofuels, can't ferment xylose.

"In contrast to S. cerevisiae, many cellulolytic fungi including N. crassa naturally grow well on both the cellulose and hemicellulose components of the plant cell wall," Cate says. "By using functional genomics data and N. crassa knockout strains, we identified separate pathways used by N. crassa to consume the cellodextrins and xylodextrins released from plant cell walls by its secreted enzymes."

To enable the N. crassa metabolic pathways to work in yeast, Cate and his collaborators introduced five new genes into the yeast. READ MORE and MORE (Ethanol Producer Magazine) Abstract (eLife)