Researchers Modifying Corn With Genes to Produce Enzymes to Enable Simpler Production of Cellulosic Ethanol
08 April 2008
Researchers at Michigan State University (MSU) are modifying the corn genome to enable the production of enzymes, within the corn biomass, needed to convert cellulose into fermentable sugar. This capability reduces the need for pretreatment of the biomass for the production of cellulosic ethanol. The transgenic corn plants produce these enzymes only in their leaves and stalk, and store them in sub-cellular compartments (the vacuoles).
The most recent version of the engineered corn—Spartan Corn III—now uses three enzymes from different sources: the thermophilic Acidothermus cellulolyticus E1 endo-cellulase; the fungal Trichoderma reesei (CBH1) exo-cellulase; and, the most recent addition, the microbial Butyrivibrio fibrisolvens H17c beta-glucosidase. MSU professor of crop and soil science Mariam Sticklen is presenting a talk on her team’s work at the 235th national meeting of the American Chemical Society this week in New Orleans, Louisiana.
The fact that we can take a gene that makes an enzyme in the stomach of a cow and put it into a plant cell means that we can convert what was junk before into biofuel.—Mariam Sticklen
The first version of the corn—Spartan Corn I—added the endo-cellulase enzyme that cuts the cellulose into large pieces. Spartan Corn II added an exo-cellulase enzyme that breaks the cellulose pieces created by the first enzyme into sugar pairs.
Spartan Corn III uses the beta-glucosidase enzyme produced by a gene from the microbe in a cow’s rumen to separate pairs of sugar molecules into simple sugars. These single sugars are then readily fermentable into ethanol.
The DNA assembly of the animal stomach microbe required heavy modification in the lab to make it work well in the corn cells.
There are a lot of changes. We have to increase production levels and even put it in the right place in the cell.—Mariam Sticklen
If the cell produced the enzyme in the wrong place, then the plant cell would not be able to function, and, instead, it would digest itself. One of the targets for the enzyme produced in Spartan Corn III is the vacuole of the cell. The enzyme will collect in the vacuole with other cellular waste products.
Because it is only in the vacuole of the green tissues of plant cells, the enzyme is only produced in the leaves and stalks of the plant, not in the seeds, roots or the pollen.
Sticklen’s research was funded by the US Department of Energy and Edenspace Systems Corp., the Consortium for Plant Biotechnology Research, and MSU Research Excellence Funds. The work will also be presented in the article “Plant Genetic Engineering for Biofuel Production: Towards Affordable Cellulosic Ethanol” in the June edition of Nature Reviews Genetics.
Modifying the corn genome to meet the US biofuel agenda (ACS National Meeting, CINF 66)
This is good news for cellulosic ethanol/biofuel production.
Could a similar approach be used to make switchgrass and other fast growth perenial plants better feed stocks for cellulosic ethanol/biofuel production?
Posted by: Harvey D | 08 April 2008 at 08:13 AM
Given that environmental extremist groups have burned down buildings and destroyed fields in their opposition to genetically modified crops, I hope those MSU researchers are taking precautions to safeguard their data.
Posted by: Alex Kovnat | 08 April 2008 at 09:26 AM
Not great, corn still uses lots of pesticides and what will you say when this corn makes it into our food supply? Genetic Foods is bad, very bad! We need to stop tinkering with mother nature and start conserving.
Posted by: Jeffrey | 08 April 2008 at 09:54 AM
So, I don't get it. If the goal is to help increase the production of cellulosic ethanol, why not do this experiment with a non-food crop that's less harmful to the soil and the water ways, such as switch grass? Besides, mucking about with transgenic corn strikes me as an incredibly stupid and short-sighted thing to do. Once the transgenic genes gets into corn crops intended for human consumption, the price of that corn will plummet.
Everyone keeps claiming that transgenic corn is "prefectly safe", but if you had a choice of buying perfectly good nontransgenic corn and corn that has been mucked with, which one would you buy?
Besides, we have a horrible record of coming up with "perfectly safe" products that are later on discovered to have adverse side-effects on our health or on the ecosystem. How long would it take before we come up with a "prefectly safe" transgenic gene that does something totally unexpected?
Posted by: Bob | 08 April 2008 at 10:06 AM
It sounds like "RoboCorn" to me ....
Posted by: Monkey Man | 08 April 2008 at 10:07 AM
Corn needs too much nitrogen and phosphorus. If they did this with Miscanthus (and the enzymes would still be in the ex-vacuoles after the stems died back), they'd really have something.
Posted by: Reality Czech | 08 April 2008 at 10:07 AM
These researchers have lost the focus of the goal, which is to not use food crop for Bio-fuels, and instead produced a product for the corn lobby. This is a counter-productive move!
Posted by: Lulu | 08 April 2008 at 10:20 AM
A far more useful approach would be to leave food for use as, well, food, and look to fast-growing trees (possibly gengineered), such as poplars, silver maples, and willows. These can produce biomass with far less input of fertilizer and insecticides, plus less fuel used for harvesting because you cut each tree once every 6 or 7 years, not every season.
Posted by: Lou Grinzo | 08 April 2008 at 10:39 AM
1. These researchers know a lot about corn, and/or get a lot of funding for corn, so they come up with a "quick, save the corn ethanol tax incentives" angle.
2. So, the vacuoles contain the cellulase enzymes that we're not sure how to manufacture cheaply enough to make cellulosic ethanol affordable (without pyrolisis). Maybe that's good for non-food plants. My concern is that maybe these plants that contain the stuff of their own decay will rot in the field. It's probably manageable, but evolutionarily it is a big disadvantage, and I would think they will be outcompeted by other varieties.
Posted by: Healthy Breaze | 08 April 2008 at 10:55 AM
"...if you had a choice of buying perfectly good nontransgenic corn and corn that has been mucked with, which one would you buy?"
That may be why they did not require labeling on food made with genetically modified crops. They may have thought that people would not buy the products and the corporations would not recover their investment and lose money.
Posted by: sjc | 08 April 2008 at 10:59 AM
From the article:
"The transgenic corn plants produce these enzymes only in their leaves and stalk, and store them in sub-cellular compartments (the vacuoles)."
This is (stover, not corn) waste to energy cellulosic ethanol. I suppose this initial study was on corn because you-know-who funded it. But now that they've isolated the genes for the appropriate enzymes, the same transgenic technique will work with other plants including say, switchgrass.
Posted by: David Anderson | 08 April 2008 at 11:06 AM
Great work. I believe the goal is to utilize the leaves and stalk in the production process not the corn itself. Good to see MSU combining its leading plant science efforts with its strong engineering program.
Posted by: Neil | 08 April 2008 at 11:11 AM
They work with corn because they understand corn genetics. No doubt a number of groups are planning on doing this in cane and switchgrass, using different localization within the plant. This is a very sound approach albeit with the genetic engineering safety issues abounding.
Posted by: matt wecker | 08 April 2008 at 12:13 PM
modern corn has very little to do with mother nature.. it has been gene-tinkered a lot
Posted by: Herm | 08 April 2008 at 12:55 PM
What happens if the farmer decides to plow the stover under to improve his soil? (Maybe there's a glut on ethanol, or the genes have escaped into feed corn.)
The cellulose will get broken down into simple sugars in the ground. Pest insects love simple sugars. There will be an infestation of aphids etc, requiring heavy applications of insecticide.
Rather spend the money buying these enzymes from a factory, and leave them out of the crops.
Posted by: Martin B | 08 April 2008 at 02:20 PM
Neil has it right - this is an attempt to use corn for a two'fer, fuel and food. Who could do a back of the envelope on how it changes the economics?
Posted by: gearhead | 08 April 2008 at 02:46 PM
That is a good point. We know from the StarLink corn example that corn pollen drifts on the wind across fields. So much for keeping the genetically modified crops isolated. Then when the farmer wants to use some of that cross pollened corn for seed, the corporations take him to court over patent infringements.
This just sounds like they are putting the enzymes in the corn stalks. I see no need to do this. Pretreatment and enzymes in the factory will do a fine job. It comes down to the phrase that just because they can do it does not mean that they should do it. Good science exercise, but to not deploy this.
Posted by: sjc | 08 April 2008 at 02:52 PM
Asides of the genetic problem we have to keep in mind that using corn stover and leave to make cellulosic ethanol will requires more fertiler (in particular phosphorus and potassium) since today the corn stover arae left in the field retuning the minerals to the soil. Using leaves and corn stover will require to balance this deficit. Again no silver bullet. Fast growing tree are better in that regard since their roots plumge deep in the soil pulling minerals from deeper ground layers
Posted by: Treehugger | 08 April 2008 at 08:40 PM
The production of ethanol from corn stover does not consume phosphorus or potassium; any of these elements in the stover will be left in the dregs of the fermentation process and can be recycled, either directly or after further processing (use in animal feed, gasification, or some such.)
Posted by: Paul F. Dietz | 09 April 2008 at 02:52 AM
I look at corn harvesting being a one pass process. The corn goes in one bin and the stalks go in another. The stubble and roots remain in the land. After they process the stalks and cobs, the carbon and other items can go back to the land. If that reduces the amount of nitrogen fertilizer, all the better.
Posted by: sjc | 09 April 2008 at 10:36 AM
Why can't they just grow some other plant that does not have such high fertilizer demands, and throw it all in the gasifier and make ethanol with the resulting CO and H2? Is it not economical compared with this complicated ethanol fermentation process?
Posted by: MarkBC | 10 April 2008 at 12:15 PM
Good question Mark. I would say because they go with what works now and are not pushing what will work tomorrow.
Posted by: sjc | 10 April 2008 at 03:59 PM
Nature has produced a plant world that is mostly cellulose because it is much harder for their enemies, mainly bugs, to digest than starches and sugars. Now this team proposes to introduce the enzymes that solve this difficult problem of digestion in none other than the location where it is pre-positioned for digestion already when the crop is in the open field.
I envision that what would happen, sooner or later, with a country covered with these crops is that some bug would hit on a way to take advantage of those enzymes in its stomache and you would have an infestation as sudden and massive as a locust plague. With results comparable to the Irish potato famine, for our alternative energy industry. Likely mother nature would get some help from OPEC's terrorist friends. Farmers would respond with massive application of pesticides.
Seed companies might not see a big problem, since they have all been bought out by chemical companies that make pesticides.
I also suspect that while the researchers are talking up the application of biofuels, which is easier to digest politically, they really have their eye more on making cheap cellulosic crops that can be fed to non-ruminant livestock with little or no processing. Otherwise I don't see what the big attraction is versus the more sensible approach of adding the cellulose-unlocking enzymes in the bioreactor, using microbes like the original cow-derived ones to make the enzymes.
For all that, I can see a positive justification for this research. Because they are pursuing such a dissimilar way of making the enzymes from others, this can be an enzyme manufacturing method of last resort to kick off the biofuels industry in case oil companies bury the patents on all the others. Enzyme-making plants could be grown in sterile greenhouses if necessary. This would help ensure the inevitability of a timely strong biofuels industry. A multipronged alternatives development effort can make it too obvious if obstructionists are closing ranks. You still need a watchdog for this, though.
Posted by: P Schager | 13 April 2008 at 05:42 AM
Is there enough fertile land to produce all the cellulosic fuel required for 4 to 5 billion gas guzzlers + (all other ICE vehicles, ships, trains, aircraft etc) and food for 8 to 10 billion humans + pets & domesticated animals + cattle + fish farms + wild animals etc?
Aren't we heading for a compromise between agrofuel and food production in many countries?
A few large countries with relatively low population density like Brazil, Argentina, USA, Canada, Russia, Australia & a few African countries etc have enough land to satisfy both requirements.
However, this may not be the case for 100+ other countries.
Agrofuel may not be a worldwide sustainable solution for the majority.
A certain (high) level of vehicle electrification may be unavoidable in the near future. If liquid fuel consumption is not curtailed, and more food stock is converted to liquid fuel, food prices will reach unaffordable level for many. Hungry people are not always rational and may not understand nor accept why many people drive agrofuel guzzlers while they are starving.
We should give a better example by accellerating development of lighter more efficient PHEVs and BEVs and get rid of our addiction for unnecessary aberrantly large gas guzzlers. Simultaneously, we should stop current and future oil wars.
We need a very strong policy statement from our leaders followed by appropriate laws and regulations by our law makers.
Posted by: Harvey D | 13 April 2008 at 10:48 AM
Harvey D. explained it perfectly. It's sad our elected officials will never understand. We need to conserve and protect our food supply. We are already seeing the effects of rapidly rising food prices around the globe.
Posted by: Ray | 18 April 2008 at 09:10 AM