Fungus produces food for humans, animals from ethanol stillage

By Holly Jessen | July 20, 2011

Researchers at Iowa State University regularly eat their work—and not because they have to—it tastes good. They add a little flour as a binder, cook it up and add veggies and spices for flavor. “Oregano and hot peppers really make it interesting,” Hans van Leeuwen, researcher and professor at Iowa State University told EPM.

What are they eating? It’s a high-quality, high protein animal feed that could someday be sold as a low-cost food product for humans. Researchers are producing a fungus, Rhizopus oligosporus, that, while growing in thin stillage from ethanol production, produces the new feed product and cleans the water, which can then be recycled back into the fuel production process.

Researchers call the feed product MycoMeal. It’s bland tasting and quite healthy. “(It’s) much better than tofu as the fungal biomass, because of the filaments, has a structure like meat, resulting in a better mouth feel,” van Leeuwen said.

The project has now been moved from a laboratory to a pilot plant that includes a 20-foot high reactor at Iowa Energy Center's BECON facility in Nevada, Iowa. Work on the pilot scale has shown researchers that process works more efficiently in batches of up to 350 gallons than it did on lab scale. Besides having two patents pending, the project has won several awards, including a 2011 Honor Award in University Research from the American Academy of Environmental Engineers.

Funding for the project is being provided by a three-year, $450,000 grant from the Iowa Energy Center, of which one year is remaining, as well as a Smithfield grant from the Office of the Iowa Attorney General, van Leeuwen said. Other supporting organizations include Lincolnway Energy LLC, a 55 MMgy ethanol plant in Nevada, Cellencor Corp. of Ames, Iowa, and Iowa State's Center for Crops Utilization Research and BioCentury Research Farm.

The ethanol production process results in five gallons of stillage for every gallon of ethanol produced. Although most of the solids are removed by centrifugation and are sold as distillers grains, the stillage does contain solids, organic compounds and enzymes. About 50 percent of the thin stillage is recycled back into the ethanol production, leaving the remainder to be evaporated and blended with distillers grains to make dried distillers grains with soluables.

Researchers at ISU, however, developed a process of adding fungus to the thin stillage, which grows into a thick mass in less than a day. About 60 percent of the organic material and most of the solids are removed, leaving cleaned water for the ethanol production process. The harvested fungus is rich in protein, certain essential amino acids and other nutrients. It can be sold as a feed product or blended with DDGS to add value and make it more suitable for feeding hogs and chickens. “The animal feed/food created is of a much higher quality than the syrup condensed from thin stillage,” he said. “As the amino acid mix remedies some deficiencies in DDG, it could be used to add value. The ultimate benefit may be heading to the health food market or general nutrition.”

At the pilot plant level, researchers have been working to evaluate oxygen requirements, an important factor since aeration is the largest operational cost. The good news is that air requirements are at least three times less than what was thought at lab scale. The group has also been working on a better screening process to harvest the product. At pilot scale screening is continuous and can also be extended for better dewatering of the product, another important factor as drying is the second largest operational cost.

One of the benefits of this process is energy savings. The technology has the potential to save U.S. ethanol producers up to $800 million a year in energy costs. It could also produce another $800 million yearly in revenue for an additional coproduct, depending on how it is used and marketed. "The MycoMeal process could truly revolutionize the biofuels industry," he said.  

Also on the research team are Nick Gabler and Mike Persia, assistant professors of animal science; Mary Rasmussen, a post-doctoral research associate in food science and human nutrition; Daniel Erickson, Christopher Koza and Debjani Mitra, graduate students; and Brandon Caldwell, a graduate of Iowa State.