Initial studies show a fungus grown in the leftovers of ethanol production could provide an energy feed source for pigs.

In feeding trials, nursery pigs were fed high-protein fungi that Iowa State University researchers produced in a pilot plant that converts ethanol leftovers into food-grade fungi.

So far in the feeding trials, researchers have found pig performance wasn’t impacted when dried fungi were substituted for corn or soybean meal. Researchers are still studying the effects of the feed on amino acid availability, tissue growth and intestinal health.

Here’s how the process works. For every gallon of ethanol produced, there are about 5 gallons of leftovers known as stillage, which contain solids and other organic material. Most of the solids are removed by centrifugation and dried into distillers’ dried grains with solubles.

The remaining liquid, known as thin stillage, still contains some solids, a variety of organic compounds and enzymes. Because the compounds and solids can interfere with ethanol production, only about 50 percent of thin stillage can be recycled back into biofuel production. The rest is evaporated and blended with distillers’ dried grains.

Iowa State researchers added fungus (Rhizopus microsporus) to the thin stillage, which it feeds and grows into easily harvested pellets in less than a day. The fungus is then harvested and dried as animal feed that is rich in protein, certain essential amino acids, polyunsaturated oils and other nutrients. It can be blended with DDGS to boost its value as a livestock feed as well as make it more suitable for feeding hogs.

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