Design of Metabolic Engineering Strategies for Maximizing L-(-)-Carnitine Production by Escherichia coli. Integration of the Metabolic and Bioreactor Levels
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- 作者：A. Sevilla ; J. Vera ; Z. Dí ; az ; M. Cá ; novas ; N. V. Torres ; and J. L. Iborra
- 刊名：Biotechnology Progress
- 出版年：2005
- 出版时间：April 2005
- 年：2005
- 卷：21
- 期：2
- 页码：329 - 337
- 全文大小：268K
- 年卷期：v.21,no.2(April 2005)
- ISSN：1520-6033
文摘
In this work metabolic engineering strategies for maximizing L-(-)-carnitine productionby Escherichia coli based on the Biochemical System Theory (1-3) and the IndirectOptimization Method are presented (4). The model integrates the metabolic and thebioreactor levels using power-law formalism. Based on the S-system model, the IndirectOptimization Method was applied, leading to profiles of parameter values that arecompatible with both the physiology of the cells and the bioreactor system operatingconditions. This guarantees their viability and fitness and yields higher rates ofL-(-)-carnitine production. Experimental results using a high cell density reactor werecompared with optimized predictions from the Indirect Optimization Method. Whentwo parameters (the dilution rate and the initial crotonobetaine concentration) weredirectly changed in the real experimental system to the prescribed optimum values,the system showed better performance in L-(-)-carnitine production (74% increase inproduction rate), in close agreement with the model's predictions. The model showscontrol points at macroscopic (reactor operation) and microscopic (molecular) levelswhere conversion and productivity can be increased. In accordance with the optimizedsolution, the next logical step to improve the L-(-)-carnitine production rate will involvemetabolic engineering of the E. coli strain by overexpressing the carnitine transferase,CaiB, activity and the protein carrier, CaiT, responsible for substrate and producttransport in and out of the cell. By this means it is predicted production may beenhanced by up to three times the original value.