Itaconic Acid Production in Escherichia coli By Overexpression of Citrate Synthase, Aconitase, and Cis -Aconitate Decarboxylase

Interest in sustainable development has led to efforts to replace petrochemical-based monomers with biomass-based ones. Itaconic acid (IA) is a C5-dicarboxylic organic acid, which can be polymerized at a high conversion rate, and as such, a building block for the chemical industry with many potential applications. To make production of these biobased building blocks competitive over their petrochemical counterparts, microbial processes have to reach high yields (g/g) and productivities (g/l/h).

IA has traditionally been produced by Aspergillus terreus, but as the process has not reached cost-efficiency in large scale, also recombinant production hosts such as Escherichia coli have been investigated. In the work of  Li et al. (2011), a key gene for itaconate biosynthesis, cis-aconitate decarboxylase (cadA) from A. terreus was successfully expressed in E. coli, but product titre remained low.

The purpose of our work was to study the IA production mechanism and thus increase the efficiency of the pathway in E. coli. We started by optimizing cadA expression conditions and also improved the availability of the precursors citrate and cis-aconitate by overexpression of heterologous citrate synthase and aconitase. As a result, IA production in E. coli was significantly improved, up to 750 mg/L, which is among the highest titres reported for this organism.