Central metabolic pathway modification to improve L-tryptophan production in Escherichia coli

Bioengineered. 2019 Dec;10(1):59-70. doi: 10.1080/21655979.2019.1592417.

Abstract

Tryptophan, an aromatic amino acid, has been widely used in food industry because it participates in the regulation of protein synthesis and metabolic network in vivo. In this study, we obtained a strain named TRP03 by enhancing the tryptophan synthesis pathway, which could accumulate tryptophan at approximately 35 g/L in a 5 L bioreactor. We then modified the central metabolic pathway of TRP03, to increase the supply of the precursor phosphoenolpyruvate (PEP), the genes related to PEP were modified. Furthermore, citric acid transport system and TCA were upregulated to effectively increase cell growth. We observed that strain TRP07 that could accumulate tryptophan at approximately 49 g/L with a yield of 0.186 g tryptophan/g glucose in a 5 L bioreactor. By-products such as glutamate and acetic acid were reduced to 0.8 g/L and 2.2 g/L, respectively.

Keywords: L-tryptophan; PEP; central metabolic pathway; metabolic engineering.

MeSH terms

  • Acetic Acid / metabolism
  • Batch Cell Culture Techniques
  • Bioreactors
  • Citric Acid / metabolism
  • Citric Acid Cycle / genetics
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins / genetics*
  • Escherichia coli Proteins / metabolism
  • Fermentation
  • Gene Expression Regulation, Bacterial*
  • Glutamic Acid / metabolism
  • Humans
  • Industrial Microbiology / methods
  • Kinetics
  • Metabolic Engineering / methods*
  • Phosphoenolpyruvate / metabolism
  • Plasmids / chemistry
  • Plasmids / metabolism
  • Transformation, Bacterial
  • Tryptophan / biosynthesis*

Substances

  • Escherichia coli Proteins
  • Citric Acid
  • Glutamic Acid
  • Phosphoenolpyruvate
  • Tryptophan
  • Acetic Acid

Grants and funding

This work was supported by the Tianjin Municipal Science and Technology Commission [Grant 17YFZCSY01050].