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Researchers Modify Bacterium to Produce Ethanol Directly with High Yield

31 May 2006

Researchers from the Universidad Nacional Autonoma de Mexico have genetically engineered the bacterium Bacillus subtilis to ferment glucose sugar directly to ethanol with a high (86%) yield. This is the first step in their quest to develop bacteria that can breakdown and ferment cellulose biomass directly to ethanol.

In a presentation at last week’s 106th General meeting of the American Society for Microbiology, the team members described their work in engineering the bacterium to produce ethanol as a single fermentation product from the sugars resulting from the breakdown of plant cellulose into simple carbohydrates.

With its very efficient secretion systems, B. subtilis is widely used in the production of extracellular hydrolytic enzymes, but it does not produce ethanol. The researchers engineered in the ethanol production capability by using the pyruvate decarboxylase (PDC) and alcohol dehydrogenase B (ADHII) from Zymomonas mobilis, a bacterium that does produce ethanol.

Initially, the team found that the integration of the ethanol synthetic pathways allowed ethanol production with a 50% yield, but with a large amount of butanediol still produced. Further tweaking avoided the butanediol formation, and bumped the ethanol yield up to 86%.

They found, however, that while the yield was high, the rate of production from the recombinant strains was low. Further work is necessary to increase the rate.

Beyond that, the next step is to engineer the bacterium to produce the cellulase enzymes that can also initially break down the stems and leaves into the simple carbohydrates required for fermentation.

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May 31, 2006 in Biotech, Ethanol | Permalink | Comments (15) | TrackBack (3)

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Comments

Ah, the wonders of genetic engineering. Wish they'd tried butanol instead, though.

Agreed, butanol, not ethanol, unless for mixing with biodiesel for NOX reduction.

We've long had organisms capable of producing ethanol from sugar, of course: brewer's yeast etc. The advance here is the yield of ethanol vs. other metabolic products.

The harder part will probably be getting the cellulase gene to work as well. However, such next-generation designer superbugs must stay where they belong, i.e. in purpose-designed bioreactors. If they were to escape, what would stop them from from munching their way through wild plants and food crops? Murphy's Law has a way of striking every technology ever devised by man.

Perhaps someone with a biology background could chime in here and clarify if this is a real risk or I'm just being paranoid.

Again, I agree with Rafael. This bacteria (virus?) scares me, if it were to "escape". With all the sick terrorists in this world today we need to worry about the security of this. Perhaps there are failsafe measures that can be implemented, and we have nothing to fear.

But I also do not think ethanol is our best answer at this point. Butanol perhaps, but butanol is so far behind ethanol, and does not have the major corn belt lobbyists working for them like ethanol.

Excuse my ignorance, but does this mean that we can get ethanol without distillation, thus cutting way back on the required energy inputs. It would be nice if we didn't have to fire up all those coal fired plants for what we like to inappropriately call green renewable energy.


To clarify the biology,
1) the ethanol produced would still have to be distilled away from the culture, so there's no evidence (yet) that using B. subtilis instead of the usual yeast or xymomonas is an advantage, but it does increase the options

2) The engineered bacterium (not a virus) doesn't pose a threat even if released. B. subtilis is ubiquitous in the environment already, and the engineering won't make it capable of "munching . . through wild plants and food crops". Even the best engineered cellulose degraders can't do anything to cellulose that hasn't been substantially pretreated. And there are a lot of natural fungal cellulose-chewing organisms that don't do any harm. They spend their days chewing up fallen trees and such. Furthermore, most organisms that are engineered to produce a single product (like ethanol) are severely compromised in their ability to survive in the wild where adaptability is key.
This is a very different situation from, say, herbicide resistant GMOs and such, where the engineering is designed to make them survive better.

Thanks Andrew, I stand corrected. But I am still worried about anyones ability to "genetically engineer" anything. Just a phobia I have, I guess.

Humans have been practicing "genetic engineering" for thousands of years. That is why we have mules. Genes from donkeys were mixed with genes from horses.

Transgenic work is what's new, mixing genetic code from completely incompatible species, and what poses a threat are the plants that breed with natural varieties and pollute the gene pool. If at some point in the future it is discovered that one of the transgenic crops causes long term damage (or even short term problems like allergies) then it's virtually impossible to eliminate because of natural crossbreeding that happens with farming. It has the potential to wipe out organic farming completely by genetic pollution.

And to add to the nightmare if your crop gets pollinated by a transgenic crop and has the properties of the GM crop you can be sued by Monsanto (or whoever owns the patent) because you don't have a licence to use their genetic code, and this is the reality for thousands of independent farmers wherever GM crops are grown.

olha so que legal

olha so que legal

olha so que legal

They would still have to do distillation, but they could use solar thermal energy to do it.

@tom deplume,

Indeed, breeding is a form genetic engineering we have been doing for thousands of years. But it is genetic engineering with nature's safeguards in place. You can only cross breed tightly related species. And the result is offspring that is slightly different from it's parents.

With modern genetic engineering, we circumvent nature's safeguards and freely mix genetic material of all species. The advantages are clear: we can produce life forms that were previously thought impossible, and achieve the desired results much, much quicker. But it comes with a risk, because the results are not always as predictable as we would like.

Because of Murphy's law the question is not whether it will go wrong, but when and how serious it will be.

Yes, I am also concerned about taking genetically engineered corn and releasing those molecules in such large quantities into the open air. We just don't know what might happen. There is very little natural corn left now since they introduced GE corn. We dumped a lot of it into Mexico since Europe and other countries around the world refused to take it (even willing to pay WTO fines to avoid).

Knowing how the GE technology works (same technology as biowarfare), I just don't believe that it is coincidence that we've had animal diseases skipping at much more alarming rates than they used to occur since we starting the GE crops around the mid 80s. The GE technology forces the skipping to occur and then it's possible that the molecules of that organism carry on the same ability to skip from plant to animal kingdom or between species that normally would not share diseases. We shouldn't be putting man-made viruses or bacteria into our food. And perhaps we shouldn't turn food made in such a way into our fuel source. If there are natural ways to get the same result - why not do that if this is not some way for Monsanto to do even more harm to the world's natural ecosystem.

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