| Conjugated linoleic acid(CLA) has a lot of important physiological funcations, and has becomed a trend as food additive. Nowsday, the CLA having the biological activity is mainly transformed by the biological synthesis. But because of the substrate linoleic acid(LA) slightly solubled in water and the CLA difficultly separated from solvent, the application of the CLA is limited. In the present dissertation, extraction by supercritical CO2(SCCO2) fluid and transformation by immobilized linoleic acid isomerase of CLA from wheat germ oil were studied. The results were as follows:On the basis of the clearly composition of the wheat germ, the extracting condition of the SCCO2 extraction wheat germ oil was pressure 30MPa, temperature 35℃, extraction time 1h, flow rate of CO2 0.5L/min. Under this condition, the yield of the wheat germ oil was 8.68%. The acquired wheat germ oil had high VE and low lipoxidase activity. These can both reduce the speed of the lipid oxidation. The POV was 64.52 mmol/kg after accelerate oxidative. These showed that the wheat germ oil had good the stability of accelerate oxidative.The calcium alginate-embedding method was chosen for the immobilized materials and methods of the linoleic acid isomerase in SCCO2 system. The preparation condition was the concentration of the sodium alginate 3%, added enzyme 20%(v/v), the concentration of the CaCl2 3%, immobilized time 4h. The activity of the immobilized linoleic acid isomerase was 38.72U/g, and the protein yield was 94.91%. The optimal substrate concentration was 70mg/ml, the optimal temperature was 35℃, the optimal pH was 6.0. The immobilized enzyme had good thermal stability. The kinetics of the LA isomerase was Km=15.30mg/ml, Vm=64.94μg/min·ml. The kinetics of the immobilized LA isomerase was Km=14.68mg/ml, Vm=45.66μg/min·ml. The activity of the immobilized LA isomerase was still 30.57U/g after repeated 3 times.The immobilized LA isomerase had good stability in SCCO2 system. The reaction condition of the enzymatic synthesis was optimized through a single factor experiment and the response surface method. The optimun reaction conditions was:LA substrate concentration 0.05g/ml, temperature 36℃, pressure 30MPa, catalytic time 1.5h. And the actual synthetic CLA was 60.58mg/g under this conditions. The synthesis quntity of the CLA still was high after repeating reaction 3 times.The conditions of the enzymatic the wheat germ oil’s LA was as follows:the concentration of the wheat germ oil 0.10g/ml, the quantity of immobilized enzyme 0.5g/ml, catalytic time 60min, the quantity of the synthsis CLA was 18.43mg. The influence of the wheat germ oil extraction and the synthsis CLA was significant with different mixed ways of immobilized enzyme and wheat germ. The water of the immobilized enzyme bonded with wheat germ in SCCO2 system. The water molecules package the wheat germ arrested the solution of the wheat germ oil in SCCO2 system. The condition of extration and enzymatic simultaneously in a kattle was the water content of the immobilized enzyme 90%, the mixed way of immobilized enzyme above the wheat germ. Under this condition, the extraction was 8.43%, the synthesis of the CLA was 2.73mg. |
PDF Full Text Request