Synthetic biology has allowed scientists to tweak E. coli to produce fuels from sugar and, more sustainably, cellulose
The bacteria responsible for most cases of food poisoning in the U.S. has been turned into an efficient biological factory to make chemicals, medicines and, now, fuels. Chemical engineer Jay Keasling of the University of California, Berkeley, and his colleagues have manipulated the genetic code of Escherichia coli, a common gut bacteria, so that it can chew up plant-derived sugar to produce diesel and other hydrocarbons, according to results published in the January 28 issue of Nature. (Scientific American is part of Nature Publishing Group.)
“We incorporated genes that enabled production of biodiesel—esters [organic compounds] of fatty acids and ethanol—directly,” Keasling explains. “The fuel that is produced by our E. coli can be used directly as biodiesel. In contrast, fats or oils from plants must be chemically esterified before they can be used.”
Perhaps more importantly, the researchers have also imported genes that allow E. coli to secrete enzymes that break down the tough material that makes up the bulk of plants—cellulose, specifically hemicellulose—and produce the sugar needed to fuel this process. “The organism can produce the fuel from a very inexpensive sugar supply, namely cellulosic biomass,” Keasling adds.
The E. coli directly secretes the resulting biodiesel, which then floats to the top of a fermentation vat, so there is neither the necessity for distillation or other purification processes nor the need, as in biodiesel from algae, to break the cell to get the oil out.