Nutritional Improvement of Corn Ethanol Co-products via Yeast Engineering

University of Minnesota/Bo Hu

Co-products generated from corn ethanol biorefining, for instance, Distiller’s Dried Grains with Solubles (DDGS), are very attractive in animal feeds as partial replacement of some more expensive and traditional feeding materials for energy (corn), protein (soybean meal), and phosphorus (monoor di-calcium phosphate). However, variability in nutrient content and digestibility, especially the lower digestibility of most amino acids compared to corn and soybean meal, has been observed, and extra undigested nutrients are then excreted to the manure, causing environmental concerns.

The project will focus on improving the nutritional value of corn ethanol coproducts by increasing the level of several key amino acids, such as lysine, tryptophan and arginine. This will be accomplished by genetic engineering of the yeast Saccharomyces cerevisiae to accumulate a higher content of key amino acids in the cell biomass during the ethanol fermentation, thereby increasing these amino acids in the final co-products. Improving the nutritional amino acid balance of such ethanol coproducts would minimize the cost associated with nutrient supplements and decrease the discharge of nitrogen to the environment.

Corn ethanol co-products are serving significant roles in the global feed market and they have become a more important revenue source for the ethanol industry. The proposed project will improve the utilization of co-products with more nutritionally balanced components and will benefit the animal feed industry and corn growers.