Engineered Microbes Boost Ethanol

Researchers at MIT have created a new strain of yeast that tolerates high levels of ethanol and ferments sugars more efficiently, making more ethanol and doing it faster.

The advance could lead to smaller, cheaper ethanol manufacturing plants, as well as reduce the notoriously high amounts of energy needed to make ethanol.
The result, described in the current issue of Science, is also an important advance in the wider effort to make organisms that can convert cheap biomass, such as corn leaves and stalks, agricultural waste, and fast-growing plants including willow and switchgrass, into ethanol. Ethanol from such sources is widely agreed to be the key to making this biofuel economically competitive with fossil fuels.

Researchers hope to engineer a single organism that will both break down the cellulose in these sources into sugars and ferment them to produce ethanol. The work by MIT chemical-engineering professor Gregory Stephanopoulos and his colleagues focuses on the second part of this process: fermenting sugars to make ethanol. The yeast strain they made can tolerate ethanol concentrations as high as 18 percent–almost double the concentration that regular yeast can handle without quickly dying. In addition, the new strain makes about 20 percent more ethanol by processing more of the glucose, and it speeds up fermentation by 70 percent.

Technology Review