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The work will be reported in the Dec. 8 issue of
Science.
Fuels such as E85, which is 85 percent ethanol, are
becoming common in states where corn is plentiful; however, their use
is mainly confined to the Midwest because corn supplies are limited
and ethanol production technology is not yet efficient enough.
Boosting efficiency has been an elusive goal, but
the researchers, led by Hal Alper, a postdoctoral associate in the
laboratories of MIT chemical engineering professor Gregory
Stephanopoulos and Whitehead Member Gerald Fink, took a new approach.
The team targeted two proteins that belong to a
class of proteins called transcription factors. These proteins
typically control large groups of genes, regulating when these genes
are turned on or shut off.
When the researchers altered a transcription factor
called the TATA-binding protein, it caused the over-expression of at
least a dozen genes, all of which were found to be necessary to elicit
an improved ethanol tolerance. As a result, that strain of yeast was
able to survive high ethanol concentrations.
In addition, this altered strain produced 50
percent more ethanol during a 21-hour period than normal yeast.
The prospect of using this approach to engineer
similar tolerance traits in industrial yeast could dramatically impact
industrial ethanol production, a multi-step process in which yeast
plays a crucial role. First, cornstarch or another polymer of glucose
is broken down into single sugar (glucose) molecules by enzymes, then
yeast ferments the glucose into ethanol and carbon dioxide.
Last year, four billion gallons of ethanol were
produced from 1.43 billion bushels of corn grain (including kernels,
stalks, leaves, cobs, husks) in the United States, according to the
Department of Energy. In comparison, the United States consumed about
140 billion gallons of gasoline. |
