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| Kinetics model for enzymatic hydrolysis of eel protein |
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ZHANG Zhiguo, WANG Junhong, CHEN Xinfeng, ZHOU Ligen, GAO Haiyan* |
| Institute of Food Science, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China |
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Abstract Kinetics model for enzymatic hydrolysis can serve as the theoretical basis for process control, and it helps to develop efficient procedures of bioactive peptides preparation through protein hydrolysis. The enzymatic hydrolysates from eel protein were demonstrated to be effective in antioxidation and inhibition of αamylase in vitro, and could be exploited as resources of antidiabetic drugs and healthy food. So far, no data on the kinetics model for enzymatic hydrolysis of eel protein can be found.
To elucidate the kinetic characteristics of enzymatic hydrolysis of eel protein, the hydrolysis of eel protein at 50 ℃, pH=7.2, with different initial concentrations of the eel protein ［S0］(0.25, 0.33, 0.50 g/mL) and different concentrations of the neutral protease ［E0］(3.33, 6.67, 10.00, 13.33 mg/mL) was preformed. The degree of hydrolysis (DH) of the eel protein was determined during a 240minute time course at varied time intervals. A kinetic model that took into account of enzyme inhibition by product or substrate was fit to the experimental data with nonlinear regression methods, and the parameters of the kinetic equation were estimated. The established kinetic equation was tested by comparing the predicted and actual DH values with paired ttest, when hydrolysis was conducted at 50 ℃, pH=7.2, and the initial concentrations of eel protein and neutral protease were 0.20 g/mL and 5.33 mg/mL, respectively.
The results showed that the DH values increased rapidly within the first 30 minutes, after which the hydrolysis rate slowed down gradually. At 240 min, the DH values increased with the rise of the neutral protease concentrations, while decreased as the initial concentrations of the eel protein increased. The kinetic equation of eel protein hydrolysis was as follows: DH=1-(1+32.65［E0］/［S0］·t-0.1t)-0.061 9. The critical concentration of the neutral protease was 3.06×10-3［S0］, and the critical concentration of the eel protein was 326.50［E0］. During the 240 min hydrolysis, no significant difference was found between the actual and predicted by this kinetic equation DH values.
In conclusion, both substrate inhibition and product inhibition existed during the eel protein hydrolysis catalyzed by neutral protease. There are critical concentrations for substrate and protease. The enzymatic hydrolysis will be impeded when the initial concentration of the eel protein is higher than the critical concentration, or the neutral protease concentration is lower than the critical concentration. The kinetic equation can fit the experimental data well, and can be used to predict the eel protein hydrolysis with neutral protease.
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Published: 20 March 2013
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鳗鱼蛋白酶解动力学模型
为阐明鳗鱼蛋白酶解动力学特性，研究在不同初始底物质量浓度［S0］和酶质量浓度［E0］条件下，中性蛋白酶对鳗鱼蛋白的酶解过程，将水解实验结果用推导的动力学模型方程进行拟合，建立酶解动力学模型. 结果表明：在50 ℃、pH=7.2的条件下酶解，鳗鱼蛋白的水解度（degree of hydrolysis, DH）随中性蛋白酶质量浓度的增大而升高，但随初始底物质量浓度的增大而降低；中性蛋白酶催化水解鳗鱼蛋白的动力学方程为：DH=1-(1+32.65［E0］/［S0］·t-0.1t) -0.061 9；酶解的最低临界中性蛋白酶质量浓度为3.06 × 10-3［S0］，最大临界底物质量浓度为326.50［E0］. 该动力学模型对实验结果有很好的拟合度，可为酶解反应过程预测提供理论依据.
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