Production of structured lipid containing docosahexaenoic and caprylic acids using immobilized Rhizopus delemar lipase

Triglycerides with medium-chain fatty acids at the 1- and 3-positions and functional fatty acids at the 2-position are referred to as structured lipids. An attempt was made to produce a structured lipid containing docosahexaenoic and caprylic acids using 1,3-positional specific Rhizopus delemar lipase, which was Immobilized on a ceramic carrier by coprecipitation with acetone. When a reaction mixture containing 5 g tuna oil and 10 g caprylic acid, 0.6 g immobilized lipase, and 0.3 g water was incubated at 30 degrees C for 2 d with shaking, acidolysis proceeded effectively but hydrolysis occurred simultaneously. This hydrolysis could be repressed by omitting water from the subsequent reaction mixture. The immobilized lipase could be reused 14 times without any significant loss of activity, and approximately 65% of the fatty acids at the 1- and 3-positions in the tuna oil were exchanged for caprylic acid. All the triglyceride products contained one or two caprylic acid molecule(s). Docosahexaenoic acid bound at the 1(3)-position in tuna oil was not exchanged because of the low activity of the R. delemar lipase on it.