DisplayTitle

Enhancing Water Removal from Whole Stillage by Enzyme Addition During Fermentation

¹Department of Chemical Engineering, Washington University, St. Louis, MO. ²United States Department of Agriculture, Agricultural Research Services, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. ³Corresponding author. Phone: 215-836-3756. Fax: 215-233-6406. E-mail address: David.Johnston@ars.usda.gov

The removal of water from coproducts in the fuel ethanol process requires a significant energy input. In this study, the addition of commercially available cell-wall-degrading enzymes was investigated to determine whether or not the enzymes could reduce the amount of water bound within the wet grains. This would have the effect of allowing more water to be removed during centrifugation, reducing the time and energy needed during the drying process. The experiment screened 15 cell-wall-degrading enzyme preparations. A significant reduction in water-binding capacity was found for a number of enzymes tested in the initial screening. The experiment was repeated and two enzymes were identified to have the highest whole stillage dewatering effect, 15 and 14% more water removed for enzyme preparations A and G, respectively. Adding different enzyme preparation amounts to the mash showed varying effects, with the potential to allow for an optimization of enzymes cost and energy savings. In some cases, an enzyme dosage of 0.5 mL worked as well, if not better, than a dosage of 1 mL. These results can translate into improvements in the overall energy efficiency of the process because the wet grains entering the drier would contain less moisture than in the conventional process thus requiring a shorter residence time in the drier.