Effect of co-products of enzyme-assisted aqueous extraction of soybeans, enzymes, and surfactant on oil recovery from integrated corn-soy fermentation

Integrated corn-soy fermentation, utilizing co-products of soybean enzyme-assisted aqueous extraction process (EAEP) of soybeans in corn fermentation, has shown potential for enhancing bioethanol production compared to corn only fermentation. To maximize economic returns, oil may be recovered. In the present study, the effect of skim and insoluble fiber, and oil extraction aids on ethanol yield, oil partition, and oil recovery, and quality of Distillers Dried Grains (DDG) was investigated. Two fiber hydrolyzing enzymes (pectinase and cellulase), an acid protease (Fermgen®), and a surfactant (Tween 80) were evaluated. Addition of skim, mixture of skim and insoluble fiber, or Fermgen® to corn fermentation resulted in a ∼32 h decrease in fermentation time. Addition of soy co-products also resulted in ∼10-28% increase in oil partition in thin stillage with no additional enzyme or surfactant treatment. Addition of insoluble fiber alone resulted in ∼19% decrease in solids partition in thin stillage. Maximum free oil recovery, 22.5 ± 4.5%, was achieved from corn-insoluble fiber thin stillage with a combined treatment of enzymes (pectinase, cellulase, and Fermgen®) and surfactant (Tween 80). Maximum extractable oil recovery, 67 ± 3.2%, was achieved with the enzyme treatment alone. Corn-soy DDG has ∼11% higher protein, ∼2% lower fiber, and ∼2% lower fat contents compared to corn DDG. The fiber content was further reduced to ∼2% after enzyme treatment. This study demonstrates an efficient use of soy EAEP co-products and enzymes to maximize oil partition in thin stillage, and produce a high quality corn-soy DDG.