The Enrichment of Docosahexaenoic Acid from Microalgal Oil by Urea Complexation via Rotary-evaporation Crystallization.

Urea complexation is a widely used method for enriching polyunsaturated fatty acids, and cooling is the traditional approach for urea crystallization. This study aimed to investigate the potential of rotary-evaporation under vacuum as an alternative method for urea crystallization in urea complexation to enrich docosahexaenoic acid (DHA). DHA-containing microalgal oil was converted to ethyl esters (EE) as the raw material. In comparison to cooling, rotary-evaporation crystallization, as a post-treatment method for urea complexation, led to higher DHA contents in the non-urea included fractions. The ratios of urea to EE converted from DHA-containing microalgal oil was found to be the primary factors influencing urea complexation when using rotary-evaporation crystallization. Through an orthogonal test, optimal process conditions were determined, including a urea/EE ratio of 2, an ethanol/urea ratio of 7, and a rotary-evaporation temperature of 75℃. Under these conditions, a concentrate containing more than 90% DHA could be obtained.