【作者】 张静；

【导师】 张嗣良；

【作者基本信息】 华东理工大学 ， 生物化工， 2012， 硕士

【摘要】 本文采用scale-down反应器模拟工业生产中的溶氧梯度,对scale-down方法的可行性进行了验证,同时以谷氨酸发酵为对象研究溶氧非均匀性对生理代谢的影响。该方法为放大过程研究提供了一种新的研究手段。首先采用单室scale-down反应器系统模拟大规模反应器内的溶氧浓度梯度,重点研究溶氧波动范围0-30%,波动周期2h、4h、6h条件下,溶氧浓度梯度对谷氨酸棒杆菌生长及其代谢的影响。结果表明在溶氧周期性波动条件下,谷氨酸棒杆菌更倾向于利用葡萄糖产生菌体而非积累产物谷氨酸,同时周期性的厌氧环境导致副产物乳酸大量积累。为了更好的模拟大规模反应器中溶氧非均匀环境的真实情况建立了双室scale-down反应器。通过实验测定与CFD模拟相结合的方法对双室scale-down反应器的流场特性进行研究,结果表明在反应器主体区与PFR部分之间形成了明显的溶氧差异,满足在实验室规模反应器内建立大规模反应器中溶氧非均匀环境的要求。最后采用双室scale-down反应器进行谷氨酸发酵,结果表明在溶氧非均匀条件下,菌体生长缓慢,但生长期延长,导致最终菌浓升高,同时谷氨酸产量下降,副产物乳酸积累,这与单室反应器中得出的结论一致。同时实验结果证明在双室scale-down反应器内存在溶氧梯度,为scale-down方法的建立奠定了基础。更多还原

【Abstract】 In this paper, the dissolved oxygen gradient occurred in industrial production was simulated in the scale-down reactors, and its results verified the feasibility of scale-down method. At the same time the effect of dissolved oxygen heterogeneity on physiology of Corynebacterium glutamincum for glutamic acid fermentation was studied. The results showed that the scale-down method provided a new research tool for the study of bioprocess scale-up.Firstly, a laboratory scale one-compartment scale-down system was used to simulate dissolved oxygen (DO) gradients occurred in large-scale. The study was mainly focused on the influences of fluctuated DO (switch between 0% and 30% with cycle time ranging from 2h to 6h) on cell growth and metabolism of Corynebacterium glutamicum. It was shown that C. glutamicum preferred to use glucose for growth but not for product accumulation under oscillating DO condition, with much more byproduct, lactate, being produced at the same time.In order to better simulate DO heterogeneous environment of large-scale bioreactor, two-compartment scale-down reactors was designed. The flow characteristics of two-compartment scale-down reactors were studied by experiment combined with CFD simulation. It was shown that DO is significantly different between the main bulk of the reactor and the PFR part. DO heterogeneity occurred in large-scale reactor was achieved in this system.Finally, the glutamic acid fermentation was done in two-compartment scale-down reactors. It was found that DO heterogeneous conditions resulted in slower cell growth rate, longer growth period, and finally higher cell concentration. Meanwhile the glutamic acid production increased but lactate accumulation decreased. They were consistent with conclusions drawn in one-compartment scale-down reactors. Meanwhile it verified that the DO gradient occurred within the reactors, and provided the foundation for the establishment of scale-down method.更多还原