Systems-Oriented Strategy for Succinic Acid Production in E. coli

Systems metabolic engineering is a growing field that brings together the principles of systems biology, synthetic biology, and evolutionary engineering. It involves applying omics data and simulation approaches for synthetic biology and systems biology for strain designing and improving processes. The combination of these concepts was successfully applied for the metabolic engineering of industrial strains. Systems Metabolic engineering could undoubtedly exploit the maximum production of microbial cell factories(Chubukov, Mukhopadhyay, Petzold, Keasling, & Martín, ۲۰۱۶). Thanks to the abundance of genetic tools available, fast cell growth, and simple culture medium, E. coli has taken as one of the most researched strains for succinate production. Strategies in E.coli's metabolic engineering can be categorized as four main methods: optimizing substrate or product transport, enhancing pathways directly involved in the production of succinates, eliminating pathways involving the accumulation of by-products, and their combinations. In many reports, these methods were studied and some highly efficient succinate producers were constructed(Cao, Cao, & Lin, ۲۰۱۱). Succinate is widely used in food, pharmaceutical, washing, and electroplating industries as surfactants, additives, intermediates, and chelating agents(Zhu & Tang, ۲۰۱۷). Succinate itself, like other weak organic acids, harms microorganisms. Since the constants of dissociation of these weak organic acids and the tolerance of microorganisms to inhibition of these acids are different genetic engineering strategies can also be used to modify metabolic pathways in order to reinforce the desired product pathway or specifically suppress by-product pathways(Li et al., ۲۰۱۰). Beauprez et al. (Beauprez et al., ۲۰۱۱) have modified the dicarboxylic acid transport system of E. coli to increase succinate production by ۵۵%. The latest researches reported, overexpression of genes directly involved in the succinate production pathway such as PEP carboxylase, PEP carboxykinase, pyruvate carboxylase, and malic enzyme. Millard et al. by overexpressing native PEP carboxylase, have achieved improvement in succinate production using E. coli JCL ۱۲۰۸ from ۳ g L−۱ to ۱۰.۷ g L−۱(Millard, Chao, Liao, & Donnelly, ۱۹۹۶). For industrial applications, further investigations are necessary. The solution for providing new perspectives on genetic engineering and metabolic engineering for higher production titers of succinate production could be a systems-oriented approach. In this work, we have used systems metabolic engineering techniques for selecting capable reactions to inhibit or activate in order to increase succinate production.

Keywords:

Systems Metabolic Engineering , Genome-scale model , Systems biology , Succinate