剪切应力对红豆杉细胞悬浮培养的影响及CFD模拟研究

Effects of Shear Stress on Suspension Cultures of T.chinensis var.mairei Cells and its CFD Simulation

在同轴圆筒装置的均匀剪切场中研究了不同剪切应力(0.16,0.46,0.78Pa)对悬浮培养的南方红豆杉细胞生理的短期影响.结果表明剪切应力为0.16～0.46Pa时,有利于细胞的生长和初生代谢;剪切应力为0 46～0.78Pa时,有利于细胞的次生代谢:另一方面利用计算流体力学(CFD)对20L生物搅拌釜(45°-斜向上桨(45°-PBT),桨距为(1/3)T的流场进行了三维模拟,获得搅拌釜内部的剪切场.结果表明搅拌釜内剪切应力分布极不均匀,且主要集中在搅拌桨区和尾流区,约为主流区和挡板区值的3～5倍,有时甚至高达7倍.通过将实验结果和CFD模拟相结合,预测了20L生物搅拌釜剪切应力对南方红豆杉细胞生理的影响.表明当搅拌转速小于150 r min-1时,搅拌釜内相应的剪切应力有利于细胞的生长和初生代谢;而当搅拌转速大于200 r min-1时,则不宜于南方红豆杉细胞的培养.

A uniform shear stress field was generated by using a co-axial cylinder apparatus to study the short-period effects of shear stress (t = 0.16, 0.46, 0.78Pa) on the Taxus cells physiology. Results showed that the cells grew well and the primary metabolism was vigorous when 0.16Pa<t <0.46Pa, and that the cells had the tendency to accumulate more secondary metabolites when 0.46Pa<t <0.78Pa. Meanwhile, a 3-D CFD simulation of the hydrodynamics characteristics in a 20L impeller stirred bioreactor (45-upward Pitched-Blade-Turbine, (1/3) T of the off-bottom clearance) was conducted to obtain the shear stress field inside the reactor. It could be seen that the strength of the shear stress was inhomogeneous and mainly concentrated in the impeller swept and wake flow regions, which was more than 7 times higher than that in the bulk and baffle regions. By combining the experimental results and CFD simulations, the effects of the shear stress on Taxus cells cultured in impeller-stirred reactors were predicted. Results showed that the impeller agitating speed less than 150 rmin-1 is beneficial to cell growth and primary metabolism. Whereas when the agitating speed is higher than 200 rmin-1, the magnitude of the average shear stress in the reactor will be too big and become unsuitable to cell culture.