New yeast strain ‘cuts major drawbacks of biofuel production methods’

WASHINGTON - Scientists at the University of California University of Illinois, the Lawrence Berkeley National Laboratory and the energy company BP have found a new yeast strain that eliminates many major shortcomings of current biofuel production methods.

The newly engineered yeast strain can simultaneously consume two types of sugar from plants to produce ethanol, researchers report.

One yeast Saccharomyces cerevisiae efficiently ferments sugars and in the process produces ethanol and carbon dioxide and the biofuel industry uses this yeast to convert plant sugars to bioethanol.

However, it has a drawback - it cannot use xylose, a secondary component of the lignocellulose that makes up plant stems and leaves.

“Xylose is a wood sugar, a five-carbon sugar that is very abundant in lignocellulosic biomass but not in our food. Most yeast cannot ferment xylose,” said Yong-Su Jin, a professor of food science and human nutrition at Illinois.

A big part of the problem with yeasts altered to take up xylose is that they will suck up all the glucose in a mixture before they will touch the xylose, Jin said.

“It’s like giving meat and broccoli to my kids,” he said. “They usually eat the meat first and the broccoli later.”

The yeast’s extremely slow metabolism of xylose also adds significantly to the cost of biofuels production.

Jin and his colleagues induced the yeast to quickly and efficiently consume both types of sugar at once, a process called co-fermentation.

“If you do the fermentation by using only cellobiose or xylose, it takes 48 hours. But if you do the co-fermentation with the cellobiose and xylose, double the amount of sugar is consumed in the same amount of time and produces more than double the amount of ethanol. It’s a huge synergistic effect of co-fermentation,” said postdoctoral researcher and lead author Suk-Jin Ha.

The new yeast strain is at least 20 percent more efficient at converting xylose to ethanol than other strains, making it “the best xylose-fermenting strain” reported in any study, Jin said.

The findings are described in the Proceedings of the National Academy of Sciences. (ANI)