Biosensor-driven adaptive laboratory evolution of l-valine production in Corynebacterium glutamicum

Metab Eng. 2015 Nov;32:184-194. doi: 10.1016/j.ymben.2015.09.017. Epub 2015 Oct 8.


Adaptive laboratory evolution has proven a valuable strategy for metabolic engineering. Here, we established an experimental evolution approach for improving microbial metabolite production by imposing an artificial selective pressure on the fluorescent output of a biosensor using fluorescence-activated cell sorting. Cells showing the highest fluorescent output were iteratively isolated and (re-)cultivated. The L-valine producer Corynebacterium glutamicum ΔaceE was equipped with an L-valine-responsive sensor based on the transcriptional regulator Lrp of C. glutamicum. Evolved strains featured a significantly higher growth rate, increased L-valine titers (~25%) and a 3-4-fold reduction of by-product formation. Genome sequencing resulted in the identification of a loss-of-function mutation (UreD-E188*) in the gene ureD (urease accessory protein), which was shown to increase L-valine production by up to 100%. Furthermore, decreased L-alanine formation was attributed to a mutation in the global regulator GlxR. These results emphasize biosensor-driven evolution as a straightforward approach to improve growth and productivity of microbial production strains.

Keywords: Adaptive laboratory evolution; Biosensor; Corynebacterium glutamicum; L-valine; Metabolic engineering; Transcription factor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biosensing Techniques*
  • Corynebacterium / genetics
  • Corynebacterium / metabolism
  • Corynebacterium glutamicum / genetics
  • Corynebacterium glutamicum / metabolism*
  • DNA, Bacterial / genetics
  • DNA, Recombinant
  • Directed Molecular Evolution
  • Fluorescent Dyes
  • Metabolic Engineering
  • Mutation
  • Valine / biosynthesis*


  • DNA, Bacterial
  • DNA, Recombinant
  • Fluorescent Dyes
  • Valine