February 01, 2008 | 15 Comments
College Station, Texas and Los Angeles, California [RenewableEnergyAccess.com] Two ongoing research projects are using E. coli to create two very different types of fuel. In one project, researchers have "tweaked" E. coli so that it will produce large amounts of hydrogen. In another, E. coli is being used to create higher-chain alcohols, which can be used as a gasoline substitute.
At Texas A&M, chemical engineering professor Thomas Wood has altered a strain of E.coli so that it produces substantial amounts of hydrogen. Specifically, Wood's strain produces 140 times more hydrogen than is created in a naturally occurring process.
By selectively deleting six specific genes in E. coli's DNA, Wood has basically transformed the bacterium into a mini hydrogen-producing factory that's powered by sugar. Scientifically speaking, Wood has enhanced the bacteria's naturally occurring glucose-conversion process on a massive scale.
With sugar as its main power source, this strain of E. coli can now take advantage of existing and ever-expanding scientific processes aimed at producing sugar from certain crops, such as corn, Wood said.
"A lot of people are working on converting something that you grow into some kind of sugar," Wood explained. "We want to take that sugar and make it into hydrogen. We're going to get sugar from some crop somewhere. We're going to get some form of sugar-like molecule and use the bacteria to convert that into hydrogen."
Biological methods such as this are likely to reduce energy costs since these processes don't require extensive heating or electricity," Wood said.
"One of the most difficult things about chemical engineering is how you get the product," Wood explained. "In this case, it's very easy because the hydrogen is a gas, and it just bubbles out of the solution. You just catch the gas as it comes out of the glass. That's it. You have pure hydrogen."
There also are other benefits.
As might be expected, the cost of building an entirely new pipeline to transport hydrogen is a significant deterrent in the utilization of hydrogen-based fuel cell technology. In addition, there is also increased risk when transporting hydrogen.
The solution, Wood believes, is converting hydrogen on site.
"The main thing we think is you can transport things like sugar, and if you spill the sugar there is not a huge catastrophe," Wood said. "The idea is to make the hydrogen where you need it."
In related E. coli news, researchers at the UCLA Henry Samueli School of Engineering and Applied Science have developed a new method for producing next-generation biofuels by genetically modifying E.coli bacteria to be an efficient biofuel synthesizer.
Higher-chain alcohols have energy densities close to gasoline, are not as volatile or corrosive as ethanol, and do not readily absorb water. Furthermore, branched-chain alcohols, such as isobutanol, have higher-octane numbers, resulting in less knocking in engines. Isobutanol or C5 alcohols have never been produced from a renewable source with yields high enough to make them viable as a gasoline substitute.
"These alcohols are typically trace byproducts in fermentation," Liao said. "To modify an organism to produce these compounds usually results in toxicity in the cell. We bypassed this difficulty by leveraging the native metabolic networks in E. coli but altered its intracellular chemistry using genetic engineering to produce these alcohols."
The research team modified key pathways in E. coli to produce several higher-chain alcohols from glucose, including isobutanol, 1-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol and 2-phenylethanol.
This strategy leverages the E. coli host's highly active amino acid biosynthetic pathway by shifting part of it to alcohol production. In particular, the research team achieved high-yield, high-specificity production of isobutanol from glucose.
This new strategy opens an unexplored frontier for biofuels production, both in coli and in other microorganisms.
"The ability to make these branched-chain higher alcohols so efficiently is surprising," Liao said. "Unlike ethanol, organisms are not used to producing these unusual alcohols, and there is no advantage for them to do so. The fact that they can be made by E. coli is even more surprising, since E. coli is not a promising host to tolerate alcohols. These results mean that these unusual alcohols in fact can be manufactured as efficiently as what evolved in nature for ethanol. Therefore, we now can explore these unusual alcohols as biofuels and are not bound by what nature has given us."
UCLA has licensed the technology through an exclusive royalty-bearing license to Gevo Inc., a Pasadena, Calif.-based company founded in 2005 and dedicated to producing biofuels.