Unraveling redox metabolism in Escherichia coli

Abstract

A wide variety of microorganisms are increasingly being employed for the production of a broad diversity of compounds, instead of using fossil fuel. The production of such compounds faces different challenges for an optimized production. Identifying the bottlenecks in the synthesis of such products offers the possibility to reduce these bottlenecks and increase the production efficiency. This could lead to economically feasible production of these compounds without utilizing fossil fuels. This thesis focuses specifically on the production of PHB using E. coli, by studying the redox modified metabolism.
Different metabolic pathways that might favour the flux towards PHB production were evaluated. More specifically, the bottlenecks in the synthesis and the conditions that might favor or limit its production were carefully analyzed in this thesis. The main bottlenecks in PHB production that have been identified and discussed in literature are the precursor acetyl-CoA and the co-factor NADPH. However, their role has not been entirely clarified in the field of metabolic engineering. Most studies use flux balance analysis to investigate the roles of acetyl-CoA and NADPH.
However, these analyses only provide information about the stoichiometry of a pathway with the flux distribution, while analyzing them through thermodynamics gives the specific reaction that is furthest from equilibrium and therefore a bottleneck for the synthesis of a product. In this thesis we combine both flux balance analysis and thermodynamics for understanding the pathways EMP (Embden-Meyerhof-Parnas pathway), Entner–Doudoroff pathway (EDP), and modified Embden-Meyerhof-Parnas pathway (mEMP).