Optogenetic tools have been harnessed to control fermentation by Princeton University scientists, who say their discovery can be used to enhance biosynthesis of valuable products in Saccharomyces cerevisiae. Using their new technique, the researchers produced chemicals including lactic acid and isobutanol.
"This technique allows us to control the metabolism of cells in an unprecedented way," said co-lead researcher José L. Avalos, an assistant professor of chemical and biological engineering. "It opens the door to controlling metabolism with light."
Using optogenetics allowed the researchers to switch on genes that they had added to the yeast cells. These particular genes are sensitive to light, which can trigger or suppress their activity. In one case, turning on and off a blue light caused the yeast to alternate between producing ethanol, a product of normal fermentation, and isobutanol, a chemical that normally would kill yeast at sufficiently high concentration.
In their paper published earlier this week in Nature, the researchers reported that their technique increased yeast's production of isobutanol as much as five times higher than previously reported levels.
Using light to control yeast's chemical production offers several advantages over techniques involving pure genetic engineering or chemical additives. For one, light is much faster and cheaper than most alternatives. It's also adjustable, meaning that turning it on and off can toggle the function of live cells on the spot at any point in the fermentation process (as opposed to chemicals, which generally can't be turned off once they are added.) Also, unlike chemical manipulators that diffuse throughout a cell, light can be applied to specific genes without affecting other parts of the cell.
Optogenetics is already used in neuroscience and other fields, but this is the first application of the technology to control cellular metabolism for chemical production, according to the team.
Image: In experiments, researchers used light to control yeast. Image courtesy of Sameer Khan/Fotobuddy.