More ethanol-tolerant yeast for more biofuel production

“This work goes a long way to squeezing the last drop of ethanol from sugar,” adds Gerald Fink, an M.I.T. professor of biology, member of the Whitehead Institute.

Yeast is an important component in the ethanol production process; however, high concentrations of ethanol are toxic to yeast. In order to improve the ethanol production process, researchers from the Massachusetts Institute of Technology are working to boost yeast tolerance to ethanol.

“Toxicity is probably the single most important problem in cost-effective biofuels production,” said George Stephanopoulos, the Willard Henry Dow Professor of Chemical Engineering at M.I.T.

The M.I.T. team boosted yeasts tolerance to ethanol by altering the composition of the medium in which the yeast is grown.

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Ethanol and other alcohols can disrupt yeast cell membranes, killing the cells. By adding potassium and hydroxide ions to the growth medium, the M.I.T. team grew yeast with cells that can compensate for the membrane damage.

With their ethanol-tolerant yeast, the M.I.T. researchers were able to boost ethanol production by about 80 percent. They also showed that this approach would work with commercial yeast strains and other types of alcohols, such as propanol and butanol, which are even more toxic to yeast.

“This work goes a long way to squeezing the last drop of ethanol from sugar,” adds Gerald Fink, an M.I.T. professor of biology, member of the Whitehead Institute.

Ethanol increases the porosity of the cell membranes of yeast, making it difficult for the cells to maintain their electrochemical gradients. The electrochemical gradients of a cell membrane are the differences in ion concentrations inside and outside the membrane, which produces energy that the cell harnesses to control the flow of molecules into and out of the cell.

By increasing the potassium concentration in the growth medium of yeast, the pH concentration outside the yeast cells are increased, strengthening the gradients and allowing them to survive longer. The longer yeast survives, the more ethanol it can make.

Post doc Felix Lam and graduate student Adel Ghaderi were also part of the team that developed this more ethanol-tolerant yeast.

The research was funded by the M.I.T. Energy Initiative and the Department of Energy. – EcoSeed Staff

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