Metabolic capacity estimation of Escherichia coli as a platform for redox biocatalysis: constraint-based modeling and experimental verification
Article first published online: 12 FEB 2008
Copyright © 2008 Wiley Periodicals, Inc.
Biotechnology and Bioengineering
Volume 100, Issue 6, pages 1050–1065, 15 August 2008
How to Cite
Blank, L. M., Ebert, B. E., Bühler, B. and Schmid, A. (2008), Metabolic capacity estimation of Escherichia coli as a platform for redox biocatalysis: constraint-based modeling and experimental verification. Biotechnol. Bioeng., 100: 1050–1065. doi: 10.1002/bit.21837
- Issue published online: 13 JUN 2008
- Article first published online: 12 FEB 2008
- Accepted manuscript online: 12 FEB 2008 12:00AM EST
- Manuscript Accepted: 18 JAN 2008
- Manuscript Revised: 18 DEC 2007
- Manuscript Received: 10 SEP 2007
- European Union (EFRE)
- Ministry of Innovation, Science, Research and Technology of North Rhine-Westphalia
Whole-cell redox biocatalysis relies on redox cofactor regeneration by the microbial host. Here, we applied flux balance analysis based on the Escherichia coli metabolic network to estimate maximal NADH regeneration rates. With this optimization criterion, simulations showed exclusive use of the pentose phosphate pathway at high rates of glucose catabolism, a flux distribution usually not found in wild-type cells. In silico, genetic perturbations indicated a strong dependency of NADH yield and formation rate on the underlying metabolic network structure. The linear dependency of measured epoxidation activities of recombinant central carbon metabolism mutants on glucose uptake rates and the linear correlation between measured activities and simulated NADH regeneration rates imply intracellular NADH shortage. Quantitative comparison of computationally predicted NADH regeneration and experimental epoxidation rates indicated that the achievable biocatalytic activity is determined by metabolic and enzymatic limitations including non-optimal flux distributions, high maintenance energy demands, energy spilling, byproduct formation, and uncoupling. The results are discussed in the context of cellular optimization of biotransformation processes and may guide a priori design of microbial cells as redox biocatalysts. Biotechnol. Bioeng. 2008;100: 1050–1065. © 2008 Wiley Periodicals, Inc.