γ-Linolenic acid (GLA) has the physiological functions of modulating immune and inflammatory responses. We produced structured
TAG rich in 1,3-dicapryloyl-2-γ-linolenoyl glycerol (CGC) from GLA-rich oil (GLA45 oil; GLA content, 45.4 wt%), which was
prepared by hydrolysis of borage oil with
Candida rugosa lipase having weak activity on GLA. A mixture of GLA45 oil/caprylic acid (CA) (1∶2, w/w) was continuously fed into a fixed-bed
bioreactor (18×180 mm) packed with 15 g immobilized
Rhizopus oryzae lipase at 30°C, and a flow rate of 4 g/h. The acidolysis proceeded efficiently, and a significant decrease of lipase activity
was not observed in full-time operation for 1 mon. GLA45 oil contained 10.2 mol% MAG and 27.2 mol% DAG. However, the reaction
converted the partial acylglycerols to structured TAG and tricaprylin and produced 44.5 mol% CGC based on the content of total
acylglycerols. Not only FFA in the reaction mixture but also part of the tricaprylin and partial acylglycerols were removed
by molecular distillation. The distillation resulted in an increase of the CGC content in the purified product to 52.6 mol%.
The results showed that CGC-rich structured TAG can efficiently be produced by a two-step process comprising selective hydrolysis
of borage oil using
C. rugosa lipase (first step) and acidolysis of the resulting GLA-rich oil with CA using immobilized
R. oryzae lipase (second step).
Key Words Acidolysis - borage oil - immobilized lipase - γ-linolenic acid -
Rhizopus oryzae
- selective hydrolysis - structured triacylglycerol