Effects of Addition of Hydrolyzing Enzymes during Fermentation on Characteristics of Distillers' Dried Grains with Solubles

Various hydrolyzing enzymes are used in dry-grind corn ethanol processes, mainly during liquefaction and saccharification steps, to improve yields of ethanol and/or distillers' corn oil. However, the effects of enzyme addition on characteristics of distillers' dried grains with solubles (DDGS) are not thoroughly understood. In this study, the effects of using acid-stable protease, pectinase, and cellulase enzymes during fermentation on chemical and physical characteristics of DDGS were evaluated, including in vitro digestibility using a pig digestion model. The use of a protease resulted in DDGS with a greater fiber content than the control (36% vs. 22%), as well as reduced protein digestibility (64% vs. 69%). The use of pectinase and cellulase (PC) also increased the fiber content of DDGS (29%) and significantly improved the protein content (27%) and protein digestibility (73%) compared with the other treatments. DDGS treated with hydrolyzing enzymes tended to have a darker color and lower water-holding capacity, but better amino-acid digestibility. Treatments with hydrolyzing enzymes significantly altered the composition and characteristics of DDGS, which strongly indicated that PC mix utilized is an effective combination to add during fermentation to produce high-quality DDGS without undesirable effects on ethanol production. The enzyme-treated DDGS can be an inexpensive and nutrient-rich diet supply to the porcine diets; however, effects on cattle and dairy cow diets were beyond the scope of the study.