Chiang Mai Journal of Science

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The lipases from the cloned pQE-TP811 and pQE-P1 carrying thermostable lipase genes from Bacillus stearothermophilus TP811 and P1 isolated from hot spring in Chiang Mai were used for the preparation of ethyl eicosapentaenoate (ethyl EPA) and ethyl docosahexaenoate (ethyl DHA) from fish oils. The free and immobilized recombinant lipases from both strains were used to study their kinetics of the hydrolytic activities using tuna oil and olive oil as substrates. Results showed that the pQE-TP811 lipase had hydrolytic activities on olive oil and tuna oil higher than pQE-P1 lipase. The activities of both lipases, pQE-TP811 and pQE-P1 lipases immobilized on celite 545 using p-nitrophenyl laurate as substrate were decreased about 10% and 17%, respectively but the hydrolytic activities on both oils were increased. The ethanolysis of tuna oil by both immobilized thermostable lipases were studied in comparison with 3 commercial lipases immobilized on celite 545. The highest yield of ethyl DHA from the alcoholysis was obtained using immobilized P. fluorescens PS lipase (0.39 mg/ml) followed by immobilized pQE-TP811 lipase (0.30 mg/ml). The highest yield of ethyl EPA from alcoholysis was obtained from immobilized pQE-TP811 lipase whereas immobilized pQE-P1 gave lowest yield of ethyl EPA and DHA. The immobilized pQE-TP811 had high specificity to long chain polyunsaturated fatty acid suitable for the preparation of EPA and DHA from fish oil. The operational stability study of the immobilized pQE-TP811 on ethanolysis of fish oil gave highest yield at first cycle of operation and gradually decreased until the fifth cycle. Addition of water into the system in the sixth cycle did not improve the yield. The time to complete the ethanolysis was more than 60 h.

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