Metabolic engineering of Escherichia coli to convert ethanol into L-tyrosine

Abstract

Abstract Utilizing ethanol derived from waste streams could establish shorter biosynthetic metabolic pathways to produce target metabolites, such as acetyl-CoA-derived chemicals. We have previously designed and constructed a two-step heterologous ethanol utilization pathway (EUP) in Escherichia coli that converts ethanol into acetyl-CoA derived compounds, including polyhydroxybutyrate (PHB) and prenol. In this study, we engineered E. coli to produce tyrosine efficiently by using ethanol as a major carbon source. Ethanol was converted into acetyl-CoA and then metabolized to generate biomass, provide energy, and produce tyrosine. The engineered strain produced 1.6 g/L tyrosine from 10 g/L ethanol. We hypothesized that the glyoxylate shunt was activated when ethanol was used as sole carbon source, and it was confirmed by transcriptome analysis. The key node gene aceA, encoding isocitrate lyase was upregulated 74-fold compared with the strain growing on glucose. To our knowledge, this is the first report of producing tyrosine from ethanol. The results support that ethanol has the potential to become a renewable feedstock to produce structurally complex chemicals.