How to make better biofuels? Convince yeast it is not starving

Yeast already helps make bread and beer and cranks out the biofuel ethanol, but scientists believe it can be used to create an even more efficient fuel called isobutanol.

Normally, yeast only creates a tiny amount of isobutanol. Now researchers at Princeton University have discovered a genetic switch that significantly ramps up production.

Researchers were able to increase isobutanol production by roughly five times over that of standard yeast strains by making the yeast much more tolerant to isobutanol's toxic effects. Isobutanol has about a 25% greater energy density than ethanol and is much better suited for use in vehicles than current ethanol-based fuels. It's a good thing for yeast that it only makes small amounts of isobutanol, as it is 10 times more toxic for yeast than ethanol.

But well before that toxic level is reached, isobutanol acts as a signal to a yeast cell, telling it that it's starving – kind of like how tummy rumbles alert us we need to eat. Thus notified, the yeast stops growing, ceases making additional isobutanol, and overall conserves resources.

In their new study, Princeton researchers have identified a gene involved in the starvation response by yeast to isobutanol. Deleting this gene turned out to profoundly enhance yeast's tolerance to the chemical. Freed of thinking it's missing meals when it's not, the yeast reallocated its resources into staving off toxic effects from higher-than-usual isobutanol concentrations.