Proteins can be a valuable co-product to ethanol within cellulosic biorefineries. These proteins are captured during a separate extraction step or from within the hydrolysate. However, protein extraction requires a large amount of solvent that must be removed in an energy intensive operation. In both cases, the proteins must be concentrated and purified before being sold as animal feed. Also, great care must be taken to insure that protein recovery does not significantly lower resulting ethanol yields. Ultrafiltration is an attractive method of concentration compared to salt or heat precipitation due to the ability to recycle the solvent and the lower energy requirement.

This research focuses on concentrating proteins from early cut Alamo switchgrass (Panicum vergatum) and distiller's dry grains and solubles (DDGS) released during cellulose hydrolysis and extracted as a separate process. We propose using a multi-stage simulated cross flow extraction to reduce solvent use while still maintaining protein yields during the extraction process. Transmembrane pressure, temperature, and solvent flow rate is varied within a tangential flow ultrafiltration system to determine its effects on protein recovery, concentration, and residence time. The concentrate is then analyzed for non-protein components to assess whether further purification is required. Finally, the remaining hydrolysate is fermented, and the kinetics and ethanol yield is compared to the protein-rich hydrolysate.