Researchers reported Monday that they have re-engineered a common bacteria to produce complex and energy-dense alcohols similar to the hydrocarbon compounds found in fuels such as gasoline. This is the first time these types of alcohols have been synthesized by bacteria (man-made or otherwise) in the lab.
Not only are most strains harmless, they’re turning out to be key for making the next generation of biofuels. Scientists have been studying and isolating strains of e. coli for years that can synthesize various types of biofuels from many different sources, such as plant material and garbage. But until now, these e. coli strains could only synthesize simple alcohols like ethanol. While this is a good start, the energy density and stability of these types of alcohols is relatively low, which leads to lower fuel economy in your car and the need for special handling equipment when compared to regular old gasoline.
To get around this problem, a research team housed at the University of California Los Angeles and headed by James Liao, has harnessed e. coli’s particularly active enzymatic production system and inserted some chromosomes into the bacteria’s DNA to “trick” it into making longer and longer chains of alchols with its existing “plumbing.” The result is that the modified e. coli can now produce complex and energy dense alcohols of 8 carbons in length.
Why is that important?
Gasoline is a mixture of many types of complex substances called long chain hydrocarbons. In a typical gasoline mixture these hydrocarbon chains range in length from 5 to 12 carbon atoms, with an average of about 8 (as in 'octane'). The length of these chains is the secret to gasoline’s high energy density compared to its volume as well as the reason why it’s a relatively stable liquid. In comparison, ethanol is made up of alchol chains 2 carbons in length.
That’s why the ability of this new man-made e. coli strain to synthesize long-chain alcohols in the lab is so groundbreaking. If we could use this engineered e. coli to make fuel that was nearly indistinguishable from gasoline, but do it out of non-food plant material and garbage, that would be a profound change.
Granted, the fuel produced by these organisms isn’t actually better than gas when it comes to energy density or stability. But when looked at as a whole, the fact that it’s not being mined out of the ground from organisms that have been dead and buried for hundred of millions of years is what, in my mind, makes it better than gas.
James Liao’s team has been working on this method for quite some time, and reported back in January on some initial breakthroughs. They say there is still much work to be done before the organism can start producing commercial quantities of fuel. The next step will be to get the process to a point where a development lab can take over and start optimizing it for commercial scale.
If you are so inclined, and either want to pay for access or have access through a university library, the study can be found in the most recent issue of the Proceedings of the National Academy of Sciences journal.