Optimization of the enzymatic synthesis of structured triacylglycerols rich in docosahexaenoic acid at sn -2 position by acidolysis of Aurantiochytrium limacinum SR21 oil and caprylic acid using response surface methodology

The thraustochytrid Aurantiochytrium limacinum SR21 is a promising source of docosahexaenoic acid (DHA) for human consumption as dietary supplement, replacing traditional fish oil. This work deals with the production of structured triacylglycerols (STAGs) with caprylic acid (CA) located at sn -1,3 positions and DHA at sn -2 position of the glycerol molecule. This process is conducted by acidolysis of CA and A. limacinum SR21 oil catalyzed by Lipozyme TL-IM and Lipozyme RM-IM. A central composite design with response surface was used to optimize the reaction temperature and the intensity of treatment (IOT). Statistical models adequately describe the reaction behavior (R 2 > 0.91). The optimal temperature values were 37 °C for both lipases. Additionally, IOTs of 9.02 and 7.87 g lipase h g −1 TAG were stablished for TL-IM and RM-IM, respectively. The reaction was scaled up by multiplying the amounts of A. limacinum oil, CA, lipase, and hexane (used as reaction medium) by a factor of 20 while maintaining the IOTs constant. TL-IM showed a better performance to catalyze the acidolysis reaction than RM-IM, achieving 40.8 mol% of total CA incorporated (91.2% of total incorporated at sn -1,3 positions), while the palmitic acid (PA) content at sn -1,3 positions decreased from 77.3 to 20.4 mol%. DHA represented 45.5 mol% of fatty acids at sn -2 position and 15.7 mol% of fatty acids at sn -1,3 positions. Using RM-IM, STAGs of similar composition were obtained.