Abstract
ABSTRACTEthylene glycol (EG) is an important chemical used as antifreeze and a raw material in polyester synthesis. The EG biosynthetic pathway from D-xylose with D-xylonate as key intermediate has some advantages, but showed low EG production. Here, we reconstructed and optimized this pathway in Escherichia coli. In view of the greater intracellular prevalence of NADH, an aldehyde reductase FucO using NADH was employed to convert glycoaldehyde into EG, in replacement of NADPH-dependent reductase YqhD. To suppress the accumulation of by-products acetate and glycolate, two genes arcA and aldA were knocked out. The resultant strain Q2843 produced 72 g/L EG under fed-batch fermentation conditions, with the yield of 0.40 g/g D-xylose and EG productivity of 1.38 g/L/h. The use of NADH-dependent enzyme FucO and by-product elimination significantly improved the performance of EG producing strain, which represented the highest titer, yield and productivity of EG reported so far.
Highlights
Ethylene glycol (EG) is an important platform chemical with considerable commercial value[1]
Split of 2-keto-3-deoxy- D-xylonate into glycoaldehyde and pyruvate was catalyzed by the endogenous aldolase YjhH, and the reduction of glycoaldehyde to EG was accomplished by the aldehyde reductase FucO using NADH as coenzyme[15]
Considering that NADH is more prevalent than NADPH in the cell, it is expected that this pathway will increase EG production to levels better than pathways employing aldehyde reductase YqhD, which requires NADPH as coenzyme[15]
Summary
Ethylene glycol (EG) is an important platform chemical with considerable commercial value[1]. Almost all countries have used EG as an antifreeze since the 1950s. Polyester products containing EG, including fiber, surfactants and plastics, have been applied in many fields such as the textile industry and the catering industry[2]. The global demands for EG had reached 23.6 million tons in 2014 and its consumption is expected to increase[3]. Most of the chemicals derived primarily from fossil fuels, including EG, are non-renewable and non-sustainable [4,5]. Due to the depletion of fossil resources, growing attention has been paid to biosynthesis of value-added chemicals using renewable biomass[6]
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