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题名	紫锥菊毛状根生长和菊苣酸生物合成的超声强化
作者	刘瑞
学位类别	博士
答辩日期	2011-09-30
授予单位	中国科学院研究生院
导师	刘春朝
关键词	紫锥菊毛状根 超声反应器 CFD 多孔介质 流体流动 传质
其他题名	Ultrasound-Intensified Root Growth and Cichoric Acid Biosynthesis in Hairy Roots of Echinacea purpurea
学位专业	生物化工
英文摘要	Plant hairy roots have been widely used in the production of secondary metabolites because of its stabilization of genetics, fast growth rate and high content of secondary metabolites. In order to enhance the secondary metabolite accumulation, a lot of metabolic regulation methods have been applied in the hairy root culture. Hairy roots cultured in liquid medium easily formed dense clumps which impaired the liquid mixing and dissolved oxygen mass transfer. As a result, the growth and secondary metabolism of hairy roots were limited. In this study, ultrasound was employed in Echinacea purpurea hairy root culture to trigger off the defence strategy and to reduce the oxygen limitation for enhancing the root growth and cichoric acid production. Computational fluid dynamic (CFD) method was employed to simulate the hydrodynamics and mass transfer within the hairy root clumps in a bioreactor, and it also was used to illustrate the ultrasound intensive effect on the oxygen mass transfer for improving hairy root growth and cichoric acid production. An efficient ultrasound-stimulation strategy was developed for improving the hairy root growth and cichoric acid biosynthesis in the hairy root cultures of E. purpurea. The mechanism of ultrasound effect on hairy root growth and metabolism was further discussed. Proper ultrasound strategy stimulated rolB expression, which further increased the endogenous IAA content for one time, and finally shortened the growth cycle for 5 days. The oxidative burst, characterized by rapid and transient production of reactive oxygen species such as hydrogen peroxide and superoxide anion, was triggered by ultrasound. This stimulated the activity of antioxidative enzymes and the metabolism of antioxidative compounds such as flavoniods and phenolic compounds. The marked increase of cichoric acid production in E. purpurea hairy roots was related to the increases of phenylalanine ammonium lyase (PAL) activity stimulated by ultrasound. Multiple ultrasound stimulation with intervals of 5 days produced the highest amount of cichoric acid because of the high PAL activity in the whole culture process. Ultrasound was applied to intensify the bioreactor culture process. Compared with that in the control, hairy root biomass and cichoric acid content increased after multiple ultrasound treatment for 6 min each 5 days. A two-dimensional axisymmetric CFD model based on a porous media model and a discrete population balance model was established to investigate the hydrodynamics and mass transfer behavior in an airlift bioreactor for hairy root culture. During hairy root culture process of E. purpurea, liquid and gas velocity, gas holdup, mass transfer rate, as well as oxygen concentration distribution in the bioreactor were simulated by this CFD model. Simulative results indicated that liquid flow and turbulence played a dominant role in oxygen mass transfer in the growth domain of the hairy root culture. The dissolved oxygen concentration in the hairy root clump increased from the bottom to the top of the bioreactor, which was verified by the experimental detection of dissolved oxygen concentration in the hairy root clump. Dynamic mesh model cooperated with changing Schmidt number method was employed for the simulation of ultrasound field. Simulation results and experimental data illustrated that ultrasound intensified oxygen mass transfer in the hairy root clump, which subsequently stimulated the hairy root growth and cichoric acid biosynthesis.
语种	中文
公开日期	2013-09-24
内容类型	学位论文
源URL	[http://ir.ipe.ac.cn/handle/122111/1758]
专题	过程工程研究所_研究所（批量导入）
推荐引用方式 GB/T 7714	刘瑞. 紫锥菊毛状根生长和菊苣酸生物合成的超声强化[D]. 中国科学院研究生院. 2011.

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