Enrichment of w-3 polyunsaturated fatty acids in tuna oils by immobilized lipases

Enrichment of w-3 polyunsaturated fatty acids in tuna oils by immobilized lipases

Anchalee Sarabok, M.Sc. Student in Biotech., PSU.
Suttawat Benjakul, D. of Industrial Biotech., 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

Grant : Graduate School, PSU.
Presented : The 12th Annual Meeting of the Thai Society for Biotechnology "Biotechnology : Impacts & Trends" Kanchanaburi, Thailand, 1-3 Novermber, 2000
Key words : w -3 polyunsaturated fatty acid, immobilized lipase, lipase-PS, lipase-D, lipase-OF, tuna oil

Tuna oils are rich in w -3 polyunsaturated fatty acids (w -3 PUFAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) which have various physiological functions and medi-cal applications. These benefits drew attention to enrich the w -3 PUFAs in tuna oil. Because w -3 PUFAs are sensitive to elevated temperature, extreme pH etc., lipase required mild reaction was the desire method for enrichment of w -3 PUFAs in tuna oil. The original tuna oil contained EPA 6.42% and DHA 27.18%. This work tried to enrich the w-3 PUFAs in tuna oil by immobilized lipases. Three commercial lipases, Lipase-PS (Pseudomonas sp. lipase), Lipase-D (Rhizopus delemar lipase) and Lipase-OF (Canndida rugosa lipase) selected from the literature reviews were immobilized by phy-sical adsorption on Accurel, EP-100 (particle size less than 200 mm). The immobilized lipases had activity 0.94, 1.45 and 1.31 U/mg support, respectively. Immobilized Lipase-PS was used to enrich the w -3 PUFAs of tuna oil in the free fatty acid fraction (FFA-PS) by selective hydrolysis. The opti-mal conditions for hydrolysis of tuna oil and water (1.5 : 1) mixed with 30 U of immobilized Lipase-PS/g of reaction mixture were at 45^oC for 24 h. After hydrolysis, the FFA fraction was 79.95%. The w-3 PUFAs in this fraction was 36.58% (EPA 6.50% and DHA 30.08%) accounted to 87.04% w-3 PUFAs recovery of the original tuna oil. Selective esterification was then conducted at 30oC for 20 h by stirring a mixture of 4 g FFA-PS and octanol (1 : 2 mol/mol), 1 g water and 50 U of immobilized Lipase-D/g of reactin mixture. As the result, the w-3 PUFAs content in the unesterified free fatty acid (FFA-D) fraction could be raised from 36.58 to 48.14% with 24.4% w-3 PUFAs recovery. Further-more, enrichment of w-3 PUFAs in glycerides by selective hydrolysis of tuna oil with immobilized Lipase-OF was determined. When a mixture of tuna oil and water (1 : 1 w/w) was stirred with 50 U of immobilized Lipase-OF/g of reaction mixture at 30oC for 24 h, the glycerides (Glycerides-OF) were generated 33.55% with 47.25% of w-3 PUFAs (EPA 3.81% and DHA 43.44%). The w-3 PUFAs recovery in the Glycerides-OF fraction was 47.18%. The esterification of Glycerides-OF with FFA- D to produce triglycerides rich in w-3 PUFAs by immobilized Rhizomucor miehei lipase is under investigation.

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