Cow stomach holds key to turning corn into biofuel

April 8, 2008
Cow stomach holds key to turning corn into biofuel
The graphic illustrates the process in which corn is genetically modified to produce an enzyme that unlocks the sugars bound in plant leaves and stalks to make them available for ethanol production. Credit: Gordon Shetler

An enzyme from a microbe that lives inside a cow’s stomach is the key to turning corn plants into fuel, according to Michigan State University scientists.

The enzyme that allows a cow to digest grasses and other plant fibers can be used to turn other plant fibers into simple sugars. These simple sugars can be used to produce ethanol to power cars and trucks.

MSU scientists have discovered a way to grow corn plants that contain this enzyme. They have inserted a gene from a bacterium that lives in a cow’s stomach into a corn plant. Now, the sugars locked up in the plant’s leaves and stalk can be converted into usable sugar without expensive synthetic chemicals.

“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,” said Mariam Sticklen, MSU professor of crop and soil science. She is presenting at the 235th national American Chemical Society meeting in New Orleans today. The work also is presented in the “Plant Genetic Engineering for Biofuel Production: Towards Affordable Cellulosic Ethanol” in the June edition of Nature Review Genetics.

Cows, with help from bacteria, convert plant fibers, called cellulose, into energy, but this is a big step for biofuel production. Traditionally in the commercial biofuel industry, only the kernels of corn plants could be used to make ethanol, but this new discovery will allow the entire corn plant to be used – so more fuel can be produced with less cost.

Turning plant fibers into sugar requires three enzymes. The new variety of corn created for biofuel production, called Spartan Corn III, builds on Sticklen’s earlier corn versions by containing all three necessary enzymes.

The first version, released in 2007, cuts the cellulose into large pieces with an enzyme that came from a microbe that lives in hot spring water.

Spartan Corn II, with a gene from a naturally occurring fungus, takes the large cellulose pieces created by the first enzyme and breaks them into sugar pairs.

Spartan Corn III, with the gene from a microbe in a cow, produces an enzyme that separates pairs of sugar molecules into simple sugars. These single sugars are readily fermentable into ethanol, meaning that when the cellulose is in simple sugars, it can be fermented to make ethanol.

“It will save money in ethanol production,” Sticklen said. “Without it they can’t convert the waste into ethanol without buying enzymes – which is expensive.”

The Spartan Corn line was created by inserting an animal stomach microbe gene into a plant cell. The DNA assembly of the animal stomach microbe required heavy modification in the lab to make it work well in the corn cells. Sticklen compared the process to adding a single Christmas tree light to a tree covered in lights.

“You have a lot of wiring, switches and even zoning,” Sticklen said. “There are a lot of changes. We have to increase production levels and even put it in the right place in the cell.”

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. That is why Sticklen found a specific place to insert the enzyme.

One of the targets for the enzyme produced in Spartan Corn III is a special part of the plant cell, called the vacuole. The vacuole is a safe place to store the enzyme until the plant is harvested. 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. It is only active when it is being used for biofuels because of being stored in the vacuole

“Spartan Corn III is one step ahead for science, technology, and it is even a step politically,” Sticklen said. “It is one step closer to producing fuel in our own country.”

Source: Michigan State University

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3.6 / 5 (5) Apr 08, 2008
Why all this work to turn corn into sugar? Why not just plant sugar cane or sorghum?
3.3 / 5 (3) Apr 08, 2008
Sugar Cane doesn't grow everywhere.
5 / 5 (1) Apr 08, 2008
A more interesting proposition would be to do similar genetic engineering on switchgrass or some other rapidly growing plant, which could be harvested several times per year, instead of once per year for corn.
not rated yet Apr 08, 2008
I believe sorghum will grow anywhere corn will.
not rated yet Apr 08, 2008
Grahf. There are certainly a few big advantages of switch grass or other weeds as opposed to corn. You don't have to use as much fertilizer as most of it is used to produce the corn cobs and perennials like switchgrass don't need much if any tilling so you don't erode soil as quickly as corn.

Corn has one big advantage if you put a stop to the madness of turning the food part into fuel and that is that if you're a bit careful about managing errosion(e.g. use no-till) you can take some of the corn stover waste without increasing soil errosion.
not rated yet Apr 08, 2008
Corns biggest advantage is there is an existing political infrastructure to subsidize it. Individul companies alreay know if they will benifit directly or indirectly from corn subsidies so know how much they are willing to spend lobbying. Where as switch grass may be a better alternitive for the country, existing companies do not know how much they gain from it so will not lobby for it.
not rated yet Apr 08, 2008
forget corn. corn should never, i repeat never should it have been chosen to make biofuel.
1 / 5 (1) Apr 09, 2008
In the old days, farmers used to put empty jugs with corks in the bottom of a silo and put chopped corn plant, called silage, a major fodder crop, on top. Fermentation occurs and by spring the jug would be filled, filtered by the cork, with something that made one drunk. Chickens would drink the silage drippings and get drunk, too.

Corn is a great plant for this as silage corn is designed for maximum leaf and plant size. 9' stands of silage corn are common.
1.7 / 5 (6) Apr 09, 2008
This is a bit confusing.

Cows do not easily and well digest corn; that is the reason that corn fed corns generally have continuing low grade infections, are therefore given anitbiotics on an ongoing basis, not to mention that they also generate a great deal of methane gas.

Grass fed cows do not suffer this problem.

Why, therefore, are we looking to cows for an efficient way of processing corn?

BTW, dairy cows are not corn fed; it is those that are destined for the slaughter house that are forced to eat corn, because they fatten up more quickly than do those eating grasses.

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