Red-hued yeasts hold clues to producing better biofuels

A compound that has scientists seeing red may hold the key to engineering yeasts that produce better biofuels.

A red pigment called pulcherrimin, naturally produced by several strains of wild yeasts, is synthesized in part through the same biochemical pathway that researchers hope to use to improve production of isobutanol, a promising biofuel alternative to ethanol.

In research published this week (Oct. 8, 2018) in the Proceedings of the National Academy of Sciences, a team based at the University of Wisconsin–Madison and the Great Lakes Bioenergy Research Center describe the genetic machinery that yeasts use to make pulcherrimin, which binds iron, an essential nutrient. The work is a key step toward harnessing the synthesis pathway for large-scale production of isobutanol as a biofuel.

"Compared to first-generation biofuels, such as ethanol, isobutanol has a higher energy content, blends better with gasoline, causes less corrosion, and is more compatible with existing engine technology," says GLBRC researcher Chris Todd Hittinger, a UW–Madison genetics professor who led the research. "Nonetheless, considerable barriers remain to producing this fuel sustainably from dedicated energy crops."

Yeasts typically do not produce much isobutanol under normal conditions, says David Krause, a postdoctoral fellow with GLBRC and the lead author of the new study. Most commonly studied species produce ethanol during fermentation. But since the early steps of isobutanol synthesis are the same as those used to make pulcherrimin, yeasts that naturally produce the pigment – readily identifiable by their distinctive red hue – caught the researchers' eyes.