Eliminating acetate formation improves citramalate production by metabolically engineered Escherichia coli

摘要: Citramalate, a chemical precursor to the industrially important methacrylic acid (MAA), can be synthesized using Escherichia coli overexpressing citramalate synthase (cimA gene). Deletion of gltA encoding citrate and leuC 3-isopropylmalate dehydratase were critical achieving high yields. Acetate is an undesirable by-product potentially formed from pyruvate acetyl-CoA, precursors during aerobic growth E. coli. This study investigated strategies minimize acetate maximize production in mutants expressing cimA gene. Key knockouts that minimized formation included kinase (ackA), phosphotransacetylase (pta), particular oxidase (poxB). glucose 6-phosphate dehydrogenase (zwf) ATP (atpFH) aimed at improving glycolytic flux negatively impacted cell accumulation shake flasks. In repetitive fed-batch process, ackA-pta poxB generated 54.1 g/L with yield 0.64 g/g (78% theoretical maximum yield), only 1.4 g/L 87 h. identified gene deletions reducing metabolically engineered strains. The final titer relative end process are highest reported date (a mass ratio nearly 40) without being detrimental productivity, significantly potential for this five-carbon chemical.