Researchers expand yeast's sugary diet to include plant fiber

BERKELEY — University of California, Berkeley, researchers have taken genes from grass-eating fungi and stuffed them into yeast, creating strains that produce alcohol from tough plant material – cellulose – that normal yeast can't digest. The feat could be a boon for the biofuels industry, which is struggling to make cellulosic ethanol – ethanol from plant fiber, not just cornstarch or sugar – economically feasible. "By adding these genes to yeast, we have created strains that grow better on plant material than does wild yeast, which eats only glucose or sucrose," said Jamie Cate, UC Berkeley associate professor of molecular and cell biology and faculty scientist at Lawrence Berkeley National Laboratory (LBNL). "This improvement over the wild organism is a proof-of-principle that allows us to take the technology to the next level, with the goal of engineering yeast that can digest and ferment plant material in one pot." A colony of the fungus Neurospora crassa (left) growing on cellulose and the yeast Saccharomyces cerevisiae. Sugar transporters from Neurospora that have been inserted into the yeast are tagged with green fluorescent protein. (Image: Jamie Cate and Susan Jenkins, UC Berkeley & EBI) The researchers hope to insert the same fungal genes into industrial strains of yeast that now are used to turn sugar into ethanol biofuel in order to improve the efficiency of the fermentation process. "The use of these cellodextrin transporters is not limited to yeast that makes ethanol," Cate said.