Issue Date: January 7, 2008
Alternative Pathway For Alcohol Biofuels
In an effort to advance biofuels, UCLA chemical engineers James C. Liao, Shota Atsumi, and Taizo Hanai have engineered Escherichia coli to produce C3–C5 alcohols from glucose using the bacteria's amino acid biosynthetic pathway (Nature 2008, 451, 86). These straight-chain and branched higher alcohols are more like the mix of compounds in gasoline and are expected to perform better as biofuels than ethanol. An existing industrial fermentation process generates 1-butanol using the bacterium Clostridium acetobutylicum. The researchers diverted the 2-keto acid intermediates from the amino acid synthesis into alcohol production, where they are first converted to aldehydes by 2-keto acid decarboxylases and then to alcohols by alcohol dehydrogenases. The biosynthetic pathway produces 1-butanol, isobutanol, and other alcohols, depending on the choice of the amino acid pathway, whereas the fermentation process produces only 1-butanol, Liao says. In addition, because the amino acid biosynthetic pathway is universal, the process can be transferred to other microorganisms, such as the yeast Saccharomyces cerevisiae.
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