Inactivation of polyphenol oxidase by dielectric barrier discharge (DBD) plasma: Kinetics and mechanisms
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Polyphenol oxidase (PPO) and peroxidase (POD) were extracted from a new loquat fruit cultivar (Ninghaibai) and characterised using reliable spectrophotometric methods. In both cases, the optimum pH for PPO was 4.5 and 5 for POD, and their optimum temperatures were 30 and 35°C, respectively. Both enzymes followed Michaelis-Menten kinetics, showing Km= 47.11 mmol/l for PPO with catechol as the substrate and Km = 153.00 mmol/l for POD with guaiacol as the substrate. PPO was much more thermolabile than POD, losing more than 40% of relative activity after 30 min of heating at 40°C. PPO activation energy was much lower than POD activation energy (ΔE# = 39.74 and 94.65 kJ/mol for PPO and POD, respectively): Both enzymes activities showed decreasing patterns as the compound concentration in the assay medium increased. 4-hexylresorcinol (4-HR), oxalic acid, and l-cysteine showed strongly inhibitive effects on the enzymes. Changes in L*, a*, and b* values were chosen to describe the browning of loquat pulp. Only PPO displayed a higher negative correlation with L* values, which indicated that PPO plays an important role in the browning of stored loquat cv. Ninghaibai.
Browning
Guaiacol
Catechol oxidase
Oxalic Acid
Catechol
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DBD(Dielectric Barrier Discharge) 플라즈마 액츄에이터의 설계 파라미터에 따른 특성을 연구하였다. 방전전압, 주파수, 전극의 간격, 폭, 길이, 유전체 두께에 따른 DBD 플라즈마 액츄에이터의 유속 및 소모전력을 측정하였다. 방전전압과 주파수가 클수록 유속과 소모전력은 증가하였다. 전극간격은 클수록 소모전력은 감소하면서 유속은 증가하였으나, 플라즈마 방전을 위해 높은 전압이 요구되었다. 상부전극폭은 좁을수록, 하부전극폭은 넓을수록 일정한 소모전력으로 유속을 증가시킬 수 있었다. 주어진 방전조건과 전극형상에서 DBD 플라즈마 액츄에이터의 성능을 예측할 수 있을 것으로 기대된다. Characteristics of DBD(Dielectric Barrier Discharge) plasma actuator as design parameters were investigated for plasma flow control. Flow velocity and power consumption of the DBD plasma actuator were measured according to the design parameters such as discharge voltage and frequency, gap, width and length of electrode, and the thickness of dielectric barrier. The flow velocity and power consumption increased as the discharge voltage and frequency increased. As the electrode gap increased, the flow velocity increased with decreasing the power consumption, whereas high voltage was required for the plasma discharge. The flow velocity increased as the upper-electrode width decreased, and as the lower-electrode width increased at the constant power consumption. The performance of the DBD plasma actuator can be estimated at the given discharge and geometry conditions.
Plasma actuator
Flow Control
Plasma cleaning
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Catechol
Browning
Catechol oxidase
Michaelis–Menten kinetics
Spectrophotometry
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Degradation
Nonthermal plasma
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Oxidative decomposition of phenolic compounds in Canarium album L.associated with activities of peroxidase(POD)and polyphenol oxidase(PPO),characteristic of peroxidase(POD)and polyphenol oxidase(PPO) from Canarium album L.were studied.The reaction time for POD should not exceed 8 min,and the Km value,the optimum pH,and the optimum temperature of POD for substrate guaiacol was 44.22 mmol/L,7.6 and 40 ℃,respectively.The reaction time for PPO should not exceed 8 min,and the Km value,the optimum pH,and the optimum temperature of PPO for substrate catechol was 7.25 mmol/L,7.5 and 60 ℃,respectively.In the optimal conditions,the effects of POD activity and PPO activity on Chinese olive(Tantou 23 and Makeng 22)with the greatest difference on total phenolic compounds content were studied.Results showed that the POD activity and PPO activity of Makeng 22 was both higher than Tantou 23.Among them,the POD and PPO activity of Makeng 22 was 12.44% and 27.31%,respectively,higher than that of Tantou 23.
Guaiacol
Catechol
Catechol oxidase
Oxidative enzyme
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In order to study the physiological and biochemical characteristics of pepper after inoculation the Phytophthora capsici,the changes of activity about phenylalanine ammonia lyase(PAL),polyphenol oxidase(PPO),β-1,3-Glucanase and chitinase were mensurated.The results showed that the changes of these protective enzymes'activities were remarkable difference between different resistance pepper lines.There was a positive correlation between the activities of phenylalanine ammonia lyase(PAL),polyphenol oxidase(PPO),β-1,3-Glucanase and chitinase and the pepper resistance to Phytophthora capsici.
Phytophthora capsici
Phenylalanine ammonia-lyase
Chitinase
Catechol oxidase
Glucanase
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Taking catechol and guaiacol as substrates respectively,the characteristics of polyphenol oxidase (PPO) and peroxidase(POD) from banana peel were studied by spectrophotometer. The results showed that the optimum temperature and pH of PPO were 30℃ and 5.5 respectively, Km was 22.42mmol/L, Vmax was 0.027OD420/min. The PPO was inactivated at 75℃ for 5min and the extinct condition of PPO was 20s at 100℃. In addition, the PPO isoenzymes in its mixture. The optimum temperature and pH of POD were 30℃ and 6.0, the POD was inactivated at 80℃ for 5min and the extinct condition of POD was 25s at 100℃.
Guaiacol
Catechol
Banana peel
Catechol oxidase
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Catechol
Catechol oxidase
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A two-dimensional numerical fluid model is developed for studying the influence of packing configurations on dielectric barrier discharge (DBD) characteristics. Discharge current profiles and time averaged electric field strength, electron number density, and electron temperature distributions are compared for the three DBD configurations, plain DBD with no packing, partially packed DBD, and fully packed DBD. The results show that a strong change in discharge behaviour occurs when a DBD is fully packed as compared to partial packing or no packing. While the average electric field strength and electron temperature of a fully packed DBD are higher relative to the other DBD configurations, the average electron density is substantially lower and may impede the DBD reactor performance under certain operating conditions. Possible scenarios of the synergistic effect of the combination of plasma with catalysis are also discussed.
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In this study, the crude protein extract containing PolyPhenolOxidase (PPO) and Peroxidases (POD) were extracted from medlar fruit ( Mespilus germanica L.) grown in Golestan Province, Iran. POD and PPO activities were studied using guaiacol and catechol as substrates, respectively. The effect of pH, temperature and thermal stability, inhibitors and cations were investigated. Results showed that Vmax was higher for PPO compared to the POD. The optimum pHs for POD and PPO were obtained at 6.5 and 5.5, respectively. The optimum temperature for both enzymes was 35°C. The Iranian medlar POD was more thermal stable than the PPO. Ascorbic acid had the highest inhibitory effect on both enzymes. Ca 2+ and Zn 2+ had the highest decreasing and increasing effect on both enzymes.
Guaiacol
Catechol oxidase
Catechol
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