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Researchers Use Fungus to Improve Corn Ethanol Process

Pilot-scale airlift reactor with external recycling for fungal processing of thin stillage. Spore inoculation occurred on Day 0 (left). Fungal pellets filled the reactor by Day 3 (right). Click to enlarge.

Growing a fungus in the thin stillage resulting from dry-mill ethanol production can reduce energy costs by as much as one-third, recycle more water and improve the distillers dried grains byproduct, according to a team of researchers from Iowa State University and the University of Hawai’i.

The Iowa State project is focused on using fungi to clean up and improve the dry-grind ethanol production process. That process grinds corn kernels and adds water and enzymes. The enzymes break the starches into sugars, which are fermented with yeasts to produce ethanol.

The ethanol is recovered by distillation, but there are about six gallons of stillage—which contains solids and other organic materials—left over for every gallon of fuel produced. Most of the solids in the stillage are removed by centrifugation and dried into distillers dried grains that are sold as livestock feed, primarily for cattle.

The remaining liquid, known as thin stillage, still contains some solids, a variety of organic compounds from corn and fermentation as well as enzymes. Because the compounds and solids can interfere with ethanol production, only about 50% of thin stillage can be recycled back into ethanol production. The remaining thin stillage is currently concentrated by flash evaporation—an energy-intensive process—and blended with DDG, producing DDG with solubles (DDGS).

DDGS is used for livestock feed, but is low in essential amino acids, e.g., lysine, limiting its usage, particularly for hogs and chickens.

The researchers added a fungus, Rhizopus microsporus, to the thin stillage and found it would feed and grow. The fungus removes about 80% of the organic material and all of the solids in the thin stillage, allowing the water and enzymes in the thin stillage to be recycled back into production.

The fungus can also be harvested. It’s a food-grade organism that’s rich in protein, certain essential amino acids and other nutrients. It can be dried and sold as a livestock feed supplement. Or it can be blended with distillers dried grains to boost its value as a livestock feed and make it more suitable for feeding hogs and chickens.

At current production levels, eliminating the need to evaporate thin stillage would save ethanol plants up to $800 million a year in energy costs. Adding the researchers’ fungal process would improve the energy balance of ethanol production by reducing energy inputs so there is more of an energy gain.

Allowing more water recycling would reduce the industry’s water consumption by as much as 10 billion gallons per year. Recycling enzymes in the thin stillage would save about $60 million per year.

Adding value and nutrients to the livestock feed produced by ethanol plants would grow the market for that feed by about $400 million per year.

Hans van Leeuwen, an Iowa State professor of civil, construction and environmental engineering and the leader of the research project, estimated it would cost $11 million to start using the process in an ethanol plant that produces 100 million gallons of fuel per year. But, he said the cost savings at such a plant could pay off that investment in about six months.

The Iowa State research project is supported by grants of $78,806 from the Grow Iowa Values Fund, a state economic development program, and $80,000 from the US Department of Agriculture through the Iowa Biotechnology Byproducts Consortium.

The researchers have filed for a patent on the technology and are looking for investors to commercialize the invention. The process still needs to be proven at larger scales.

Van Leeuwen, and the other researchers developing the technology—Anthony L. Pometto III, a professor of food science and human nutrition; Mary Rasmussen, a graduate student in environmental engineering and biorenewable resources and technology; and Samir Khanal, a former Iowa State research assistant professor who’s now an assistant professor of molecular biosciences and bioengineering at the University of Hawai’i at Manoa—recently won the 2008 Grand Prize for University Research from the American Academy of Environmental Engineers for the project.




Anything that improves corn ethanol's energy balance is a good thing, since I don't see us halting production. The water savings looks especially significant. And the fungus is a feed supplement to boot.

Nice going, Iowa State.

Mark A

Corn kernel ethanol should be at a dead end.....STOP THE RESEARCH!!!!!!!!! Jees.... our food supply already is under enough strain!!


Mark, what kind of comment is that? Progress is a bad thing? Like it or not, the ethanol industry is evolving at a moderate pace, and we won't have significant production levels of cellulose based ethanol for at least a few years. So, if this is a legitimate short-term improvement that can maximize the efficiency of the corn kernel source that we have, why wouldn't we promote this? These plants are already built, and this sounds like a pretty good cost to benefit ratio.....

Another thing that will improve the energy balance for ethanol production would be to use electricity from wind power instead of burning natural gas for heat generation. This is not profitable yet but time is working for wind power that drops in price and because the cost of natural gas keeps rising.


My post above.

the distillers-byproduct can also be used to feed hungry people, and to feed our fuel hungry SUVs also.. all around a winner for the world. If it feeds hogs with this new fungus it can feed people also.. it is already sterile.


It is quite reasonable to estimate that research into corn based ethanol will delay introduction of non-food based ethanol.

Perhaps we will eventually need a law to prevent the creation of fuels from food sources.


Vegemite for your chickens and pigs?


Lulu, I do not agree with you on that point. Research funding for non-food based biofuels is not lacking - it's the large-scale private capital investments to commercialize the technology that have been too slow to follow. Research such as this has no impact on that.

Also, we don't need any more laws to prohibit anything. While we do need some subsidies to get things going over the short term, pure economics will weed out the inefficient processes such as corn kernel based ethanol over time. It won't happen overnight though. There is a misconception that this is taking food out of our mouths - that is not the case. 75% of the corn that is being used is for livestock anyway, and the DDG byproduct turns out to be a much higher quality feed for most livestock anyway.

Lulu, actually most research that can bring down the cost of corn ethanol will also bring down the cost of most forms of non-food biomass ethanol. For instance, enzyme based cellulosic ethanol uses enzymes to break cellulose to sugars that can be fermented and refined using the exact same processes as corn ethanol. Even Coskata’s gasification and bioreactor technique will need processes from corn ethanol to distil the ethanol. A rough best guess is that 70% of the technology that is developed for corn ethanol will be reused for the same processes in non-food ethanol.

Furthermore, the corn ethanol factories will be extended to use non-food biomass feedstock once that is more profitable than using corn ethanol.


forgot id again


EU seems to agree with you and many countries are considering to cap grain ethanol prodcution to a sustainable level. It seems that a 5% level could be maintain with surplus grain/corn. Should that be used as a cap level?

USA may very well go much over the 5% level ( = 7 billion/gal/year requiring about 3 billion bushels of corn a year) within 2 to 3 years. If it wasn't for export, (to feed the rest of the world), USA could use 50% of it's yearly corn production (0.5 x 13 = 6.5 billion bushels) to produce about 16 billion gallons of ethanol per year. That could meet about 11.6% of the local liquid fuel required.

When 50+% of the corn production is used to feed our gas guzzlers, watch what will happen to the price of meat, bread, pasta, milk, beer, and most other edible products in many countries. It may not be very pretty.



That was from me.


"Remember personal info" doesn't seem to be working.

Anyway, when you consider that Congress has mandated more and more corn ethanol in our fuel supply, research like this is a given.


Im with Henrik, since most of the ethanol plants are in the Midwest where there is plenty of wind, why not mandate wind mills at every plant. Its a no-brainer as far as I can see.

Mad Max

It should be possible to use solar energy and/or waste heat from any thermal power plant (coal, nuclear, whatever) to improve the energy balance.

Healthy Breaze

Combining feedlots which have methane recapture with corn ethanol plants will improve the energy balance further. This technique would be additive to that. Also, by having the animals right at the plant, the distiller grain does not need to be dried, which further saves energy and labor.


A consciences is growing that fuel production from food stuffs should not be encouraged/subsidized and I agree with it.

I don’t know if GCC will mention this subject due to its controversial nature and unfortunate history, but there now may be something to it.

If it is proven true, it could be the beginning of a new era. Yes, it is my fondest dream; Cold Fusion. Sorry if it is off topic but GCC and its members should check it out. You deserve to know.




Extraordinary claims require extraordinary evidence. I have higher hopes for Polywell/Bussard Fusion. The WB-7 test article is operating right now.



The Arata system may be an easier replacement of my oil fired hot water unit because of its small size and lack of neutron radiation. The WB-7 system will take up half my basement.(-:

Some people want to prohibit anything related to what they don't like. Some people want to require everyone to do what they like. Some people hate our elected officials telling us what we can and can't do. I think these are all the same people. No wonder they are so cranky.
This type of research should be encouraged. It helps short term and might help related science (cellulosic fuel production).


Dang it. That was me.


Excellent article. Wish some could see the big picture here. We have so much farm land sitting idle now. Small farmers can not afford to plant corn. The price of oil is driving high food prices not ethanol production.


1. Process heat is a poor use of electricity, especially wind electricity. The best approach is to burn cob, it's easy to harvest and collect alongside the corn kernels. POET is building a plant in Emmettsburg Iowa which does this (they call it a cellulosic plant, but that's mostly hype).

2. Enough of this crap about how DDGS makes superior feed. Ethanol takes 2/3rds of the calories, the leftover DDGS is too high in protein and too low in carbohydrates and essential nutrients to be used in more than limited amounts. It's value as feed is significantly less than the original corn and is priced accordingly.

3. Combining feedlots and methane recapture with ethanol plants seems like a good idea. So far those who have tried it are struggling, so the jury is still out.


Speaking of ethanol, from Technology Review:

A biorefinery built to produce 1.4 million gallons of ethanol a year from cellulosic biomass will open tomorrow in Jennings, LA. Built by Verenium, based in Cambridge, MA, the plant will make ethanol from agricultural waste left over from processing sugarcane.

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