Iterative optimization of exogenous genes and redirection of metabolic flux for enhanced itaconate biosynthesis in engineered Escherichia coli

Abstract

BackgroundItaconate or itaconic acid (IA), a sustainable and valuable platform chemical, has garnered significant attention due to its potential as an alternative petroleum-derived compound. In the past, Aspergillus terreus offered a high titer of IA, but it still faced the challenges of low productivity. To overcome the problem, a fast-growing Escherichia coli BW25113 was involved consolidating the itaconate production pathway, eliminating byproduct-forming pathways, and enhancing intermediate levels to facilitate large-scale production. MethodE. coli was engineered through the deletion of isocitrate decarboxylase (Icd) and the overexpression of pyruvate carboxylase (CgPyc), cis-aconitate decarboxylase (AtCadA) and aconitate hydratase (ENAcnA) to facilitate the IA biosynthesis pathway. A B0015 terminator was encoded behind AtCadA to improve transcription efficiency as well as poxB gene was deleted to accelerate carbon influx towards the tricarboxylic acid cycle instead of forming the byproduct acetate. A semi-continuous batch fermentation approach was employed for large-scale IA biosynthesis to address ATP insufficiency in long-termed fermentation. Significant findingThe engineered strain AB15C/Δicd improved IA titer by 20 % compared to the control strain. By deleting the acetate forming pathway under acidic condition, AB15C/ΔicdΔpoxB increased itaconate production. Overexpression of ENAcnA in AB15CEN*/ΔicdΔpoxB strain resulted in 13.8 g/L of IA. Finally, a semi-continuous batch fermentation was implemented, leading to an IA accumulation of 35.5 g/L after 4 batches.