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ที่มา:วิทยาสารเกษตรศาสตร์ สาขา วิทยาศาสตร์


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The lipase enzyme extracted from defatted Thai scented rice bran with calcium chloride solution which has been purified by ammonium sulfate precipitation, followed by dialysis had the specific activity of 2.04 units/mg protein and 1.32 times that of starting crude extract. The semi-purified lipase obtained showed the optimum pH at 7.6 with equilibrium rate constants, K1 and K2, and maximum enzyme reaction rate, (EA)max of 3.2 x 10-7, 1.7 x 10-9 M and 44.2 units/ml, respectively. Based upon the enzyme kinetics of the temperature effect, the lipase enzyme had the activation energy, Ea = 11.03 kcal/mol and the energy for the thermal inactivation, ?Hd =30.8 kcal/mol. The absolute reaction rate function with the remained parameter constants estimated by non-linear regression analysis was EA = . As a result, the maximum enzyme activity of 42.7 units/ml was calculated with the mentioned equation at Tmax equal to 35oC. Moreover, the Thai scented rice bran lipase were stable over the pH range from 4 to 9 and the temperature range from 20 to 45oC, but completely lost the activity by heating at 50oC for 60 min. Finally, the model for lipase activity affected by pH and temperature was proposed and figuredly simulated to predict the enzyme activity under various pH and temperature conditions.

Article Info
Agriculture and Natural Resources -- formerly Kasetsart Journal (Natural Science), Volume 031, Issue 1, Jan 97 - Mar 97, Page 56 - 71 |  PDF |  Page