Recovery of corn oil from ethanol extracts of ground corn using membrane technology

The recovery of additional co-products from the dry-grind process for ethanol could influence the industry greatly, as most facilities today rely on subsidies and tax incentives to operate. Modification of the process to include the extraction of oil could add $0.30-0.50 per bushel to the value derived from corn. A process combining solvent extraction with membrane technology to recover the oil was investigated. To evaluate the feasibility of this process, several nanofiltration membranes were tested for their stability in ethanol. Each of the membranes was conditioned with a solution of water/ethanol (0-100 vol/vol%) and the top three were chosen based on their performance with respect to flux and rejection. Beginning at 5 g/L, solutions of corn oil in ethanol were concentrated to over 100 g/L with the DK (Osmonics-Desal, Minnetonka, MN), TFC-SR1 (Koch Membrane Systems, Inc., Wilmington, MA), and TFC-SR2 (Koch) membranes. The liquid extract was then similarly concentrated, yielding a retentate fraction that was highly concentrated with solids in addition to corn oil, such as protein (zein), lecithins, and other potentially high-value fractions soluble in ethanol. Analysis of the extract retentate showed a significant increase in oil concentration with an increase in the volume concentration ratio, indicating that pure ethanol extracts from corn may be successfully concentrated using nanofiltration membranes.