Enrichment of w-3 polyunsaturated fatty acids in tuna oils by two
enzymatic reactions with three lipases
Anchalee Sarabok, M.Sc. Student in Biotech., PSU.
Suttawat Benjakul, Asst. Prof., D. of Food Tech., F. of Agro-Industry, PSU.
Aran H-Kittikun, Asst. Prof., D. of Industrial Biotech., F. of Agro-Industry, PSU.
Corresponding e-mail : haran@ratree.psu.ac.th
Presented : The World Congresson Biotechnology, the 11th International Biotechnology
Symposium and Exhibition, Berlin, Germany 3-8 September, 2000
Key words : tuna oils, polyunsaturated fatty acids, lipases
Tuna oils are rich in w-3 Polyunsaturated Fatty Acids ( w-3 PUFAs), especially eicosapenta-enoic acid (EPA) and docosahexaenoic acid (DHA) which have various physiological functions and medical applications. EPA and DHA play an important role in the prevention of a number of human diseases such as cardiovascular diseases, inflammation and cancer. EPA and DHA are not found
in beef, pork nor all vegetables, only marine products such as fish and shellfish are rich in EPA and DHA. In particular, tuna contains large amount of EPA and DHA than the others. The original tuna
oils contained EPA 4.44% and DHA 24.24% (free fatty acids 0.11%, molecular weight approximately 909.42 g/mol). These benefits drew attention to the acids and w-3 PUFAs-rich oil which were produced as a food material by the enzymatic method. This work tried to enrich the w-3 PUFAs of tuna oils by two enzymatic reactions, selective hydrolysis and esterification. Three commercial lipases, Lipase-PS (Pseudomonas sp.), Lipase-OF (Candida rugosa) and Lipase-D (Rhizopus delemar), which have different fatty acids and positional specificities found to be suitable for concentrating w-3 PUFAs in tuna oils. When a mixture of tuna oils and water was stirred with 50 units of soluble Lipase-PS/g
of reaction mixture at 30oC for 24 hours, the w-3 PUFAs content in the free fatty acids fraction (FFA-PS) was 40.34% (986.97 g/mol). On the other hand, when tuna oils were treated with soluble Lipase-OF at the same condition resulted in the production of glycerides containing 48.93% of w-3PUFAs which named Glycerid-OF (1,196.54 g/mol). Selective esterification was then conducted at 30oC for 24 hours by stirring a mixture of 4.94 g FFA-PS, 11.96 g Glyceride-OF (1 : 2 mol/mol), 4.23 g water and 4225 units of soluble Lipase-D. As a result, triglycerides enriched in w-3 PUFAs were generated 74.47% with w-3 PUFAs content 41.14%.
These lipases were immobilized on the Accurel, EP-100 (particle size less than 200 mm). After the Accurel 500 mg which pretreated with ethanol was suspended in 50 ml of soluble Lipase-PS 7.81 mg/ml and Lipase-OF and Lipase-D 1 mg/ml, phosphate buffer pH 7 was gradually added with stirr-ing and the filtrate was dried in vacuo. The immobilized lipases had activity 0.94, 1.32 and 1.45 Units per mg support, respectively, by this procedure.
When the immobilized Lipase-PS and Lipase-OF were used in the later reaction the w-3
PUFAs content in FFA-PS was 37.78% and Glyceride-OF was 47.25%, respectively. Future work
will study optimum condition to enrich w-3 PUFAs in tuna oils by these two enzymatic reactions : amount of immobilized lipases, water content, temperature and time.
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