De novo Synthesis of 2-phenylethanol from Glucose by Metabolically Engineered Escherichia coli

Abstract

2-Phenylethanol (2- PE) is an aromatic alcohol with wide applications, but there is still no efficient microbial cell factory for 2-PE based on Escherichia coli. In this study, we constructed a metabolically engineered E. coli capable of de novo synthesis of 2-PE from glucose. Firstly, the heterologous styrene-derived and Ehrlich pathways were individually constructed in an L-Phe producer. The results showed that the Ehrlich pathway was better suited to the host than the styrene-derived pathway, resulting in a higher 2-PE titer of approximately 0.76 ± 0.02 g/L after 72 h of shake flask fermentation. Furthermore, the phenylacetic acid synthase encoded by feaB was deleted to decrease the consumption of 2-phenylacetaldehyde, and the 2-PE titer increased to 1.75 ± 0.08 g/L. As phosphoenolpyruvate (PEP) is an important precursor for L-Phe synthesis, both the crr and pykF genes were knocked out, leading to a about 35 % increase of the 2-PE titer, which reached 2.36 ± 0.06 g/L. Finally, a plasmid-free engineered strain was constructed based on the Ehrlich pathway by integrating multiple ARO10 cassettes (encoding phenylpyruvate decarboxylases) and overexpressing the yjgB gene. The engineered strain produced 2.28 ± 0.20 g/L of 2-PE with a yield of 0.076 g/g glucose and productivity of 0.048 g/L/h. To our best knowledge, this is the highest titer and productivity ever reported for the de novo synthesis of 2-PE in E. coli. In a 5-L fermenter, the 2-PE titer reached 2.15 g/L after 32 h of fermentation, suggesting that the strain has the potential to efficiently produce higher 2-PE titers following further fermentation optimization.

Effects of Environmental Stresses on Synthesis of 2-Phenylethanol and IAA by Enterobacter sp. CGMCC 5087

“…KDC4427 exhibits both phenylpyruvate decarboxylase (PPDC) and indolepyruvate decarboxylase (IPDC) activities, and can efficiently catalyze the decarboxylation of phenylpyruvic acid (PPA) and indolylpyruvate acid (IPyA) to form phenylacetaldehyde and indoleacetaldehyde, respectively. Subsequently, they are converted to 2-PE and IAA by acetaldehyde reductase and acetaldehyde oxidase, respectively [7,[18][19][20].…”