Submitted to: Biotechnology for Fuels and Chemicals Symposium Proceedings
Publication Type: Abstract only
Publication Acceptance Date: 5/3/2006
Publication Date: 5/30/2006
Citation: Ximenes, E.A., Dien, B.S., Ladisch, M.R., Mosier, N., Cotta, M.A., Li, X. 2006. Enzyme production by industrially relevant fungi growing on feed co-product from dry mill ethanol plants [abstract]. Biotechnology for Fuels and Chemicals. p. 107. Interpretive Summary:
Technical Abstract: The United States corn ethanol market has grown to 3.4 billion gal/yr (2004) and is targeted to reach 7.5 billion gal/yr by 2012. Expanding ethanol production has raised concerns about finding a sufficient market for Distillers Dried Grain with Solubles (DDGS), the major co-product produced at a dry grind facility. Currently, DDGS is sold primarily as a ruminant animal feed. In this study, DDGS was investigated as carbon source for extracellular hydrolytic enzyme production. Three microorganisms, noted for their high cellulolytic and hemicellulolytic enzyme titers, were grown on DDGS: Trichoderma reesei, Aspergillus niger, and Aureobasidium pullulans. DDGS was either used as delivered from the plant (untreated) or after being pretreated with hot-water (HW-DDGS, 20 min and 160 deg C). All three microorganisms secreted a broad range of enzymes when grown on DDGS. T. reesei and A. niger produced higher xylanase titers when cultured on HW-DDGS compared to growth on untreated DDGS, while the converse was observed for A. pullulans. Maximum xylanase titers were produced in three days for A. niger and A. pullulans and eight days for T. reesei cultures. Initial cultures were cultivated in flasks. Larger amounts of enzymes were produced in bioreactors (5 L) either equipped with rushton (for T. reesei) or updraft marine impellers (A. niger). Production titers were lower for bioreactor vs. flask cultures, especially for T. reesei cultures. Attempts to improve enzyme titers will be addressed using fed batch feeding schemes.