Chemical kinetics, thermodynamics and inactivation kinetics of dextransucrase activity by ultrasound treatment

Autor: Weibing Lan, Shan Chen
Rok vydání: 2020
Předmět:
Zdroj: Reaction Kinetics, Mechanisms and Catalysis. 129:843-864
ISSN: 1878-5204
1878-5190
Popis: In this work, the impact of ultrasound on dextransucrase activity was investigated, and a biphasic model was introduced to investigate the inactivation kinetics of the dextransucrase catalytic reaction. In addition, a chemical kinetic model, the Michaelis–Menten equation, Eyring transition state theory and the Arrhenius equation were applied. Short periods of exposure to low-intensity ultrasound significantly increased the activity of dextransucrase. The maximum activity was 1.25 ± 0.01 u/mL at an ultrasound intensity of 1.8 W/cm3 for 3 min, which was 27.6% higher than the activity of the untreated enzyme (0.98 ± 0.038 U/mL). In addition, after the ultrasound treatment, the kinetic model of the dextransucrase catalytic reaction was fitted to a first-order kinetic model at low sucrose concentrations. At low sucrose concentrations, the Ea, ΔH, ΔS and ΔG of ultrasound-treated dextransucrase were reduced by 33.7, 35.7, 28.8 and 0.38%, respectively. Furthermore, compared with the parameters of the untreated sample, the value of Vmax the treated sample increased, and Km decreased. The thermal inactivation model of the dextransucrase catalytic reaction in a shaker was fitted to a biphasic model, and the percentage of the thermally stable fraction of ultrasound-treated dextransucrase was increased, while the rate of deactivation was decreased. Moreover, the degree of thermal inactivation was inversely proportional to the dextransucrase concentration. The fluorescence spectra showed a decrease in the amount of tryptophan on the surface of dextransucrase treated with ultrasound. In conclusion, short-term treatment with low ultrasound intensity increases the activity, thermal stability and reaction rate of dextransucrase.
Databáze: OpenAIRE
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