Improved cell growth and biosynthesis of glycolic acid by overexpression of membrane-bound pyridine nucleotide transhydrogenase
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The non-conventional d-xylose metabolism called the Dahms pathway which only requires the expression of at least three enzymes to produce pyruvate and glycolaldehyde has been previously engineered in Escherichia coli. Strains that rely on this pathway exhibit lower growth rates which were initially attributed to the perturbed redox homeostasis as evidenced by the lower intracellular NADPH concentrations during exponential growth phase. NADPH-regenerating systems were then tested to restore the redox homeostasis. The membrane-bound pyridine nucleotide transhydrogenase, PntAB, was overexpressed and resulted to a significant increase in biomass and glycolic acid titer and yield. Furthermore, expression of PntAB in an optimized glycolic acid-producing strain improved the growth and product titer significantly. This work demonstrated that compensating for the NADPH demand can be achieved by overexpression of PntAB in E. coli strains assimilating d-xylose through the Dahms pathway. Consequently, increase in biomass accumulation and product concentration was also observed.
KeywordsNADPH PntAB Glycolic acid Escherichia coli Dahms pathway Cofactor regeneration
This work was supported by Korea Research Fellowship Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (2015H1D3A1062172 and 2016R1C1B1013252) and by the Ministry of Education (No. 2018R1D1A1B07043993 and No. 2009-0093816).
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Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants performed by any of the authors.
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