Production of structured TAG rich in 1,3-capryloyl-2-arachidonoyl glycerol from Mortierella single-cell oil

Two oils containing a large amount of 2-arachidonoyl-TAG were selected to produce structured TAG rich in 1,3-capryloyl-2-arachidonoyl glycerol (CAC). An oil (TGA58F oil) was prepared by fermentation of Mortierella alpina, in which the 2-arachidonyoyl-TAG content was 67 mol%. Another oil (TGA55E oil) was prepared by selective hydrolysis of a commercially available oil (TGA40 oil) with Candida rugosa lipase. The 2-arachidonoyl-TAG content in the latter was 68 mol%. Acidolysis of the two oils with caprylic acid (CA) using immobilized Rhizopus oryzae lipase showed that TGA55E oil was more suitable than TGA58F oil for the production of structured TAG containing a higher concentration of CAC. Hence, a continuous-flow acidolysis of TGA55E oil was performed using a column (18×125 mm) packed with 10 g immobilized R. oryzae lipase. When a mixture of TGA55E oil/CA (1∶2, w/w) was fed at 35°C into the fixed-bed reactor at a flow rate of 4.0 mL (3.6 g)/h, the degree of acidolysis initially reached 53%, and still achieved 48% even after continuous operation for 90 d. The reaction mixture that flowed from the reactor contained small amounts of partial acylglycerols and tricaprylin in addition to FFA. Molecular distillation was used for purification of the structured TAG, and removed not only FFA but also part of the partial acylglycerols and tricaprylin, resulting in an increase in the CAC content in acylglycerols from 44.0 to 45.8 mol%. These results showed that a process composed of selective hydrolysis, acidolysis, and molecular distillation is effective for the production of CAC-rich structured TAG.