Bioeconomy Institute

Fermentation of Biorefinery Feedstocks

The US is expected to produce more than 10 billion bushels of corn this year. More than 20% of the US crop (35% in Iowa) is processed further into ethanol, starch, oils, corn syrup, sugar and co-products. Corn contains 61% starch, 4-6% oil, 8-11% fiber and 8% protein (gluten). Both fiber and gluten end up in the corn gluten feed (12.5 lbs/ bushel) and corn gluten meal (2.5 lbs/bushel) during wet corn milling or in the 18 lbs/bushel corn distillers dried grains with solubles during dry corn milling and ethanol production. Corn contains 61% starch, 4-6% oil, 8-11% fiber and 8% protein (gluten). Both fiber and gluten end up in the corn gluten feed (12.5 lbs/ bushel) and corn gluten meal (2.5 lbs/bushel) during wet corn milling or in the corn distillers dried grains with solubles (18 lbs/bushel) during dry corn milling and ethanol production.

Yeasts including other prokaryotic microbes can certainly not degrade these substances and they are not suitable substrates for ethanol fermentation. Pretreatment of ligno-cellulosic materials using high temperature and/or acid/base pretreatments, pyrolysis, anaerobic bacterial acidification or biohydrogen production, and/or the recently developed solubilization/ depolymerization in specialized binary ionic organic solvents, is costly and have not found commercial application. The proposed research will use microbes generally known as "white rot" and "brown rot" fungi both of the class Basidiomycetes to depolymerize the complex substrates at ambient pressures and low temperatures (c. 35oC). The white rots delignify the plant biomass, whereas brown rots "enzymatically liberate" lignin by degrading cellulose. The fungal processes produce much simpler carbohydrates as breakdown products, which can be used as substrate for ethanol production in a secondary yeast fermentation process. Additionally, the fungal and yeast biomass as well as most of the residues will have good value as animal feed supplements as they are high in protein and improve the taste of other constituents.

Principal Investigators:

Johannes Van Leeuwen, Iowa State University

Anthony Pometto III, Iowa State University

Rob Anex, Iowa State University

Samir Kumar Khanal, Iowa State University 

Clark Ford, Iowa State University

Associated Contracts or Grants:

Fungal Protein and Byproducts from Corn Processing Wastewater Using Micro-Fungi
Using White and Brown Rot Fungi to Degrade Low-Value Co-products from Corn Processing Stream into Reusable Substrate

Participating and/or Sponsoring Organizations:

Iowa Biotechnology Byproducts Consortium (USDA)
Iowa Energy Center (IEC)
Archer Daniels Midland (ADM)
Procter & Gamble (P&G)