Engineered Microbes Boost Ethanol

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If their approach can modify industrial yeast, it would drive down the cost of ethanol, Ladisch says. And eventually this research could have a wider impact, he says, because the mechanism that the researchers used to make the ethanol-tolerant yeast could be used as a blueprint to develop other wanted traits in microbes. "They now have a handle into fundamental metabolic pathways in how the yeast might be modified," he says.

Stephanopoulos believes that cellulosic-ethanol yields could be improved by tailoring certain traits in microbes using his technique. It might be possible to make microbes that are tolerant of compounds other than ethanol that are created in the fermentation process and toxic to the microbes. He also hopes to produce strains that eat sugars with five carbon atoms, such as xylose, that are produced when cellulose is broken down. The microbes used in today's processes only ferment sugars like glucose that have six carbon atoms.

Much work remains to be done to develop a single organism that can first break down cellulose into sugars before fermenting these sugars. Breaking down cellulose is a key constraint to the viability of making ethanol from biomass, says Lee Lynd, professor of engineering at Dartmouth College. "The research and development-driven advances with the greatest impact on producing cellulosic ethanol at low cost and high efficiency have to do with converting biomass into sugars," he says.