Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Food Science and Human Nutrition


Food Science and Technology

First Advisor

Tong Wang

Second Advisor

Buddhi P. Lamsal


To improve the profitability of the industry, ethanol plants are capturing the values of coproducts, including distillers corn oil (DCO) and dry distillers grain with solubles (DDGS). Current oil recovery method can only recover 40% of oil contained in corn, which needs to be improved along with DDGS quality. This study explores the use of surfactants and hydrolyzing enzymes to improve oil recovery and DDGS quality. Our research has shown that the use of non-ionic surfactants in dry-grind ethanol process affected oil partition in thin stillage and improved final oil yield. The surfactant replaced protein from the emulsion interface and formed an un-stable oil-in-water emulsion, and silica nano-particle enhanced the demulsification by using surfactant. Surfactants also significantly improved the oil partition in thin stillage by washing the adhering oil from wet cake surface into liquid phase. The synergistic effect between hydrolyzing enzyme and surfactant was observed on oil recovery from condensed corn distillers solubles (CCDS). Using protease, cellulase and pectinase enzymes hydrolyzed the non-fermentable components (protein and non-starch polysaccharides) and improved ethanol production yield and increased oil partition in thin stillage. The use of protease enzyme decreased oil recovery from CCDS and this reduction can be overcome by using surfactant during fermentation step. The enzyme treatments also have significant effects on DDGS properties, especially on the digestibility. Protease enzyme treated DDGS had low protein content and protein digestibility. Whereas, pectinase and cellulase treated DDGS was easy to digest and provided higher amount of required amino acids compared to other treatments. Overall, the methods for improving DCO recovery were successfully developed and the effects of hydrolyzing enzymes on DDGS quality were also determined. The results of this research point to novel ways to modify production strategies for ethanol plants to enhance profitability.


Copyright Owner

Lei Fang



File Format


File Size

92 pages