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

Abstract

Feruloyl Soy Glyceride (FSG) is an all‐natural replacement for petroleum‐based ultraviolet 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. The effect of CO2 pressure and temperature on the solubilities of components of the FSG reaction mixture was studied to select optimized conditions for the enzymatic reaction and purification. Pressure–temperature conditions were then selected to use in a recycling system. The enzymatic products were analyzed for CO2 with and without recycling CO2. The solubilities of all components of the reaction mixture were proportional to CO2 density but the relative solubilities of individual components were not equal at all pressures and temperatures. 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. The CO2 was recycled through the reactor at 13.8 MPa (removing more FAEE by‐products) and through the receiver at 6.0 MPa (removing less FAEEs). In the recycling treatment, the material left behind in the reactor had 99.6% FSG content. The use of the reduced pressure receiver in a recycling CO2 system effectively increased the amount of EF incorporated onto the soybean oil increasing the yield of the FSG product.