Team uses cellulosic biofuels byproduct to increase ethanol yield

Scientists report in Nature Communications that they have engineered yeast to consume acetic acid, a previously unwanted byproduct of the process of converting plant leaves, stems and other tissues into biofuels. The innovation increases ethanol yield from lignocellulosic sources by about 10 percent.

Lignocellulose is the fibrous material that makes up the structural tissues of plants. It is one of the most abundant raw materials on the planet and, because it is rich in carbon it is an attractive source of renewable biomass for biofuels production.

The yeast Saccharomyces cerevisiae is good at fermenting simple sugars (such as those found in corn kernels and sugarcane) to produce ethanol. But coaxing the yeast to feast on plant stems and leaves is not so easy. Doing it on an industrial scale requires a number of costly steps, one of which involves breaking down hemicellulose, a key component of lignocellulose.

"If we decompose hemicellulose, we obtain xylose and acetic acid," said University of Illinois food science and human nutrition professor Yong-Su Jin, who led the research with principal investigator Jamie Cate, of the University of California at Berkeley and the Lawrence Berkeley National Laboratory. Jin and Cate are affiliates of the Energy Biosciences Institute (EBI), which funded the research. Jin also is an affiliate of the Institute for Genomic Biology at Illinois.

"Xylose is a sugar; we can engineer yeast to ferment xylose," Jin said. "However, acetic acid is a toxic