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Computational fluid dynamics modeling of mass-transfer behavior in a bioreactor for hairy root culture. II. Analysis of ultrasound-intensified process

Authors

  • Rui Liu,

    1. National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P.R. China
    2. Graduate School of the Chinese Academy of Sciences, Beijing 100049, P.R. China
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  • Wei Sun,

    1. Department of Information, General Hospital of Air Force, Beijing 100142, China
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  • Chun-Zhao Liu

    Corresponding author
    1. National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P.R. China
    2. Graduate School of the Chinese Academy of Sciences, Beijing 100049, P.R. China
    • National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P.R. China
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Abstract

Recently, cichoric acid production from hairy roots of Echinacea purpurea was significantly improved by ultrasound stimulation in an airlift bioreactor. In this article, the possible mechanism on ultrasound-intensified hairy root culture of E. purpurea in the bioreactor was elucidated with the help of computational fluid dynamics (CFD) simulation, membrane permeability detection, dissolved oxygen concentration detection, confocal laser-scanning microscopy (LSM) observation, and phenylalanine ammonium lyase (PAL) activity analysis. The CFD model developed in Part I was used to simulate the hydrodynamics and oxygen mass transfer in hairy root bioreactor culture stimulated by ultrasound. A dynamic mesh model combined with a changing Schmidt number method was used for the simulation of the ultrasound field. Simulation results and experimental data illustrated that ultrasound intensified oxygen mass transfer in the hairy root clump, which subsequently stimulated root growth and cichoric acid biosynthesis. Ultrasound increased the hairy root membrane permeability, and a high root membrane permeability of 0.359 h−1 was observed at the bottom region in the bioreactor. LSM observation showed that the change in the membrane permeability recovered to normal in the further culture after ultrasound stimulation. PAL activity in the hairy roots was stimulated by ultrasound increase and was correlated well to cichoric acid accumulation in the hairy roots of E. purpurea. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011

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