Using critical carbon dioxide to optimize the enzymatic transesterification of soybean oil and ethyl ferulate to feruloyl soy glycerides

Authors: Eller, Fred; Compton, David - Dave

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2023
Publication Date: 3/9/2023
Citation: Eller, F.J., Compton, D.L. 2023. Using critical carbon dioxide to optimize the enzymatic transesterification of soybean oil and ethyl ferulate to feruloyl soy glycerides. Journal of the American Oil Chemists' Society. https://doi.org/10.1002/aocs.12690.
DOI: https://doi.org/10.1002/aocs.12690

Interpretive Summary: The need for sunscreen has been widely presented to the public. Most sunscreens use petroleum-based ultraviolet absorbing ingredients. A bio-based sunscreen called Feruloyl Soy Glyceride (FSG) can be produced from soybean oil and ethyl ferulate, a natural product found in plants such as the Japanese goldthread. Researchers in Peoria, Illinois, looked at the effects of carbon dioxide pressure and temperature on the solubilities of reaction components in the end mixture. It was discovered that after cycling carbon dioxide between a high and low pressure, the FSG produced was nearly pure and free of unreacted ethyl ferulate and unwanted by-products. These results show a significant improvement to the method of FSG production over the current method.

Technical Abstract: Feruloyl Soy Glyceride (FSG) is an all-natural replacement for petroleum-based UVA and UVB absorbing ingredients currently used in sunscreens. It is produced by the Novozym® 435-catalyzed transesterification of ethyl ferulate (EF) with triglycerides. By-product fatty acid ethyl esters (FAEEs) are more soluble in CO2 than the EF and triglyceride starting materials. It was hypothesized that the preferential removal of the FAEEs over EF would drive the enzymatic reaction towards the desired FSG product. This study investigated the effect of CO2 pressure and temperature on the relative solubilities of the components of the FSG reaction mixture to select optimized conditions for the enzymatic reaction and purification. Specific pressure-temperature conditions were then selected to use in a cycling system. Enzymatic products were analyzed for CO2 without recycling, CO2 with recycling, and CO2/He with recycling. The solubilities of all components of the reaction mixture were proportional to CO2 density but the relative solubilities of individual components were not equal for all pressures and temperatures tested. At 60°C, the ratio of ethyl linoleate to EF was only 1.1 at 6.9 MPa but 3.1 at 13.8 MPa. This suggested that cycling from 13.8 MPa (to remove a higher ratio of FAEE by-products) to 6.9 MPa (to remove a lower ratio of FAEEs) could drive the equilibrium towards the desired FSG product. Cycling the CO2 through the receiver removed ca. 70% of the total material mass from the reactor. In the cycling treatments, the material left behind in the reactor had very high FSG content, 99.6 and 99.7%, with or without He added to the CO2, respectively. The use of the reduced pressure receiver in a cycling CO2 system effectively increased the amount of EF incorporated onto the glycerol backbone of soybean oil resulting in an increase in yield of the FSG product.