Constructing an ethanol utilization pathway in Escherichia coli to produce acetyl-CoA derived compounds

Abstract

AbstractEngineering microbes to utilize non-conventional substrates could create short and efficient pathways to convert substrate into product. In this study, we designed and constructed a two-step heterologous ethanol utilization pathway (EUP) in Escherichia coli by using acetaldehyde dehydrogenase (encoded by ada) from Dickeya zeae and alcohol dehydrogenase (encoded by adh2) from Saccharomyces cerevisiae. This EUP can convert ethanol into acetyl-CoA without ATP consumption, and generate two molecules of NADH per molecule of ethanol. We optimized the expression of these two genes and found that ethanol consumption could be improved by expressing them in a specific order (ada-adh2) with a constitutive promoter (PgyrA). The engineered E. coli strain with EUP consumed approximately 8 g/L of ethanol in 96 hours when it was used as sole carbon source. Subsequently, we combined EUP with the biosynthesis of polyhydroxybutyrate (PHB), a biodegradable polymer derived from acetyl-CoA. The engineered E. coli strain carrying EUP and PHB biosynthetic pathway produced 1.1 g/L of PHB from 10 g/L of ethanol and 1 g/L of aspartate family amino acids in 96 hours. We also engineered E. coli strain to produced 24 mg/L of prenol from 10 g/L of ethanol in 48 hours, supporting the feasibility of converting ethanol into different classes of acetyl-CoA derived compounds.HighlightsEngineered Escherichia coli strains to grow on ethanol as sole carbon sourceDemonstrated that ethanol was converted into acetyl-CoA (AcCoA) through two pathways (acetaldehyde-acetate-AcCoA and acetaldehyde-AcCoA)Converted ethanol into two acetyl-CoA derived products with low structural similarity (polyhydroxybutyrate and prenol)Discovered that supplementation of the aspartate family amino acids can substantially improve cell growth on ethanol