Synthesis of structured lipids containing medium-chain and omega-3 fatty acids.
The ability of different lipases to incorporate omega3 fatty acids, namely, eicosapentaenoic acid (EPA, C20:5n-3), docosapentaenoic acid (DPA, C22:5n-3), and docosahexaenoic acid (DHA, C22:6n-3), into a high-laurate canola oil, known as Laurical 35, was studied. Lipases from Mucor miehei (Lipozyme-IM), Pseudomonas sp. (PS-30), and Candida rugosa (AY-30) catalyzed optimum incorporation of EPA, DPA, and DHA into Laurical 35, respectively. Other lipases used were Candida anatrctica (Novozyme-435) and Aspergillus niger (AP-12). Response surface methodology (RSM) was used to obtain a maximum incorporation of EPA, DPA, and DHA into high-laurate canola oil. The process variables studied were the amount of enzyme (2-6%), reaction temperature (35-55 degrees C), and incubation time (12-36 h). The amount of water added and mole ratio of substrates (oil to n-3 fatty acids) were kept at 2% and 1:3, respectively. The maximum incorporation of EPA (62.2%) into Laurical 35 was predicted at 4.36% of enzyme load and 43.2 degrees C over 23.9 h. Under optimum conditions (5.41% enzyme; 38.7 degrees C; 33.5 h), the incorporation of DPA into high-laurate canola oil was 50.8%. The corresponding maximum incorporation of DHA (34.1%) into Laurical 35 was obtained using 5.25% enzyme, at 43.7 degrees C, over 44.7 h. Thus, the number of double bonds and the chain length of fatty acids had a marked effect on the incorporation omega3 fatty acids into Laurical 35. EPA and DHA were mainly esterified to the sn-1,3 positions of the modified oils, whereas DPA was randomly distributed over the three positions of the triacylglycerol molecules. Meanwhile, lauric acid remained esterified mainly to the sn-1 and sn-3 positions of the modified oils. Enzymatically modified Laurical 35 with EPA, DPA, or DHA had higher conjugated diene (CD) and thiobarbituric acid reactive substance (TBARS) values than their unmodified counterpart. Thus, enzymatically modified oils were more susceptible to oxidation than their unmodified counterparts, when both CD and TBARS values were considered.
Hamam
Fayez
F
Department of Biochemistry, Memorial University of Newfoundland, St. John's, Newfoundland, Canada A1B 3X9.
Shahidi
Fereidoon
F
D001234:Aspergillus niger / Q000201:enzymology; D002175:Candida / Q000201:enzymology; D004281:Docosahexaenoic Acids / Q000032:analysis / Q000378:metabolism; D015118:Eicosapentaenoic Acid / Q000032:analysis / Q000378:metabolism; D004951:Esterification; D005227:Fatty Acids / Q000032:analysis / Q000378:metabolism*; D015525:Fatty Acids, Omega-3 / Q000032:analysis / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000032:analysis / Q000378:metabolism; D008049:Lipase / Q000378:metabolism; D008055:Lipids / Q000096:biosynthesis* / Q000737:chemistry*; D009089:Mucor / Q000201:enzymology; D011549:Pseudomonas / Q000201:enzymology
D005227:Fatty Acids; D015525:Fatty Acids, Omega-3; D005231:Fatty Acids, Unsaturated; D008055:Lipids; D004281:Docosahexaenoic Acids; D015118:Eicosapentaenoic Acid; D008049:Lipase; C026219:docosapentaenoic acid