Scientists from the University of Illinois have reported 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. This innovation increases ethanol yield from lignocellulosic sources (aka second generation feedstocks) by nearly 10 percent. According to researchers, the new advance will streamline the fermentation process and will simplify plant breeding and pretreatment of the cellulose. The results were published in Nature Communications.
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 researchers explain that 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 is an affiliate of the Institute for Genomic Biology at the U of I.
“Xylose is a sugar; we can engineer yeast to ferment xylose,” Jin said. “However, acetic acid is a toxic compound that kills yeast. That is one of the biggest problems in cellulosic ethanol production.” Continue reading