The optimization of operating parameters for the isolation of peroxidase from horseradish (Armoracia rusticana) roots with ultrafiltration (UF) technology was systemically studied. The effects of UF operating conditions on the transmission of proteins were quantified using the parameter scanning UF. These conditions included solution pH, ionic strength, stirring speed and permeate flux. Under optimized conditions, the purity of horseradish peroxidase (HRP) obtained was greater than 84 % after a two-stage UF process and the recovery of HRP from the feedstock was close to 90 %. The resulting peroxidase product was then analysed by isoelectric focusing, SDS-PAGE and circular dichroism, to confirm its isoelectric point, molecular weight and molecular secondary structure. The effects of calcium ion on HRP specific activities were also experimentally determined.

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In the rotor system, the labyrinth seal system is the core component to suppress fluid leakage between the rotor and the stator. This paper analyzes the vibration characteristics of the coupling of air-induced vibration and crack fault. First, perform numerical simulation analysis and test verification on the response of the system with no sealing force and crack failure; Subsequently, the system with sealing force and different crack parameters was analyzed for numerical simulation analysis, and then the influence of crack damage failure on other sealing parameters (including sealing pressure difference, sealing gap, and sealing length) was studied; Finally, the influence of double crack damage (damage location, damage degree, phase difference angle) on the rotor system is analyzed. The results show that when the crack depth increases to a certain value, it will also cause the superharmonic resonance phenomenon in the subcritical speed region of the system; When the system has a sealing force, it is found that the airflow excitation frequency of the system can be affected as the degree of crack damage increases; The coupled dynamic response of airflow excitation and crack faults shows a rich spectrum of nonlinear phenomena, which is closely related to the degree of cracks and sealing parameters. Increasing the crack angle will weaken the impact of crack damage on the system. This research can provide a theoretical basis for detecting and diagnosing crack faults in the labyrinth seal rotor system.