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UCLA Researchers Modify E. Coli to Produce Efficiently Higher-Chain Alcohols for Advanced Biofuels

The UCLA approach shifts part of the bacteria’s biosynthetic pathway to alcohol synthesis. Various 2-keto acid precursors lead to corresponding alcohols through 2-ketoacid decarboxylase and alcohol dehydrogenase. Click to enlarge.

Researchers at UCLA have genetically modified Escherichia coli to produce efficiently several higher-chain alcohols from glucose, including isobutanol, 1-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol and 2-phenylethanol. A description of the work appears in the 3 January issue of the journal Nature.

Instead of relying on fermentation for the production of the alcohols, the UCLA approach—developed by professor of chemical and biomolecular engineering James Liao, postdoctoral fellow Shota Atsumi and visiting professor Taizo Hanai—leverages E. coli’s highly active amino acid biosynthetic pathway by shifting part of it (its 2-keto acid intermediates) to alcohol synthesis. In particular, the research team achieved high-yield, high-specificity production of isobutanol from glucose.

These [higher-chain] alcohols are typically trace byproducts in fermentation. 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.

—James Liao

This new strategy opens an unexplored frontier for biofuels production, both in E. coli and in other microorganisms.

The ability to make these branched-chain higher alcohols so efficiently is surprising. 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.

—James Liao

Compared to ethanol, higher-chain alcohols have energy densities closer to gasoline, are not as volatile or corrosive, 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 yet to be produced from a renewable source with yields high enough to make them viable as a gasoline substitute. The approach taken by the UCLA team offers the promise of much higher yields.

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. Liao has joined Gevo’s scientific advisory board. In this role, he will continue to provide technical oversight and guidance during the commercial development of this technology.

The research was supported in part by the UCLA–Department of Energy Institute for Genomics and Proteomics and the UCLA–NASA Institute for Cell Mimetic Space Exploration.




Yes! Great going, UCLA!


Does this sound like a process that can be cycled indefinitely...constantly adding feedstock to the broth and skimming off the C5 aclahol?

Rob McMillin

Define "efficient".


For all the butanol enthusiasts this looks promising. The source for the glucose may be an issue if this process can successfully be scaled.


Bio butanol and Rick Neuheisel too, UCLA is on a roll. Just kidding guys!


Bio butanol and Rick Neuheisel too, UCLA is on a roll. Just kidding guys!


It's worth noting that Dupont reported the production of isobutanol by this same method in a patent application published in April 2007 (US20070092957). I'm no lawyer, but it's hard to imagine how these guys can exclusively license their technology to a startup if someone else has already patented it.


I don't know enough to really say but maybe ...
Dupont can only patent their pathway (for host, application) and not the approach of using gene cutting and pasting to getting isobtanol from bacteria.

This paper talks about adding just two steps (acid -> aldehyde -> alcohol) to getting isobutanol production from E Coli. And then they made a few more changes to improve things.
From what I could guess about Dupont via, they were adding a complete (different) pathway.



It is possible UCLA claims a separate patent since they are producing four alcohol types other than isobutanol. One would hope that progress in this area is expedited beyond infringement issues.


The efficiency of this process is surprisingly high. In a starting solution of 36 grams of glucose per liter, about 12 grams of isobutanol is produced (33%) by their modified E.Coli bacteria, which is 86% of the theoretical maximum conversion efficiency of glucose to isobutanol. However, the process is rather slow as the maximum yield was produced after 5 days. At the 2-day point, only 6 grams of isobutanol were produced, about half the yield seen at the 5-day point.


looking at the data there are several problems left to be solve before this can be use in industry. First production of alcohols was in 1-.1 millimolars or concentrations far less then 1%, much higher concentrations are needed as such low concentrations are simply impracticable to distill. Second in large reactors the bacteria is going to mutate away from production of product unless a mechanism is in place to keep the inserted genes functional and active.

fred schumacher

Cellulose is a long-chain of glucose molecules. Once the right enzymes are found to snip that chain apart, we will have a new way to produce carbohydrate feedstock, both for fuel and food.

In the corn belt, perennial C4 grasses like panicum virgatum (switchgrass) and miscanthus giganteus can produce three to four times as much biomass as grain corn. These are low-fertility, low-maintenance plants. UI Urbana-Champaign field trials produced an EROI of 50 on unprocessed miscanthus, while also sequestering 4 tons per acre carbon per year.

Three-fourths of the American corn crop ends up as animal feed. If, by switching to grass, carbohydrate production is tripled over today's corn yields, then one part of the glucose produced would go to feed, and the other two parts would be available for fuel feedstock. Thus, the present corn acreage could provide both feed and fuel at the same time on the same space.

Today, on average, we use a 4,000 pound vehicle to move a 200 pound payload. If today's vehicle fleet is replaced with one more appropriate to the task, I believe a quadrupling of average fuel economy is achievable, using existing technology.

These two concepts: a moving away from annual crops to perennial crops, and an adoption of the right tool for the right task for transportation, could make for a sustainable liquid fuel future that is carbon neutral.

@ Fred,

Good thoughts.

jed Clampett

Hate to be the voice of caution in this but...

Given the safety records of our industries, are we sure we want to modify an organism as dangerous as E. Coli to be used in an industrial scale? Seems to me that an organism like E. Coli, and even more so if modified to produce higher alcohols, would be even more deadly to humans if they can produce these alcohols within the system, I doubt you would experience the good effects of alcohol, but you would sure be dead of alcohol poisoning probably even faster than what is now experienced with the bug.
Can we truly trust industry to keep such a dangerous organism contained? They can't even contain genetically modified salmon, our oceans are now contaminated with frankenfish, should we allow them to toy around with microscopic beings that would be even harder to identify and control if it escaped into the wild?


jed Clampett,

In this case the organism is being engineered to produce something, this is a serious drain to the organism and thus the organism could not compete or function against natural organisms that don't waste most of their metabolites making industrial products instead of offspring. So no this GM E.coli is not a threat, rather keeping it from mutating back to its wild type form (not producing alcohols) is the problem: keeping this organism safe from nature is the concern not keeping nature safe from this organism.

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