Genome-wide screening of transcription factor deletion targets in Escherichia coli for enhanced production of lactate-based polyesters.

Engineered Escherichia coli is a useful platform for production of lactate (LA)-based polyester poly[LA-co-3-hydroxybutyrate (3HB)] from renewable sugars. Here we screened all non-lethal transcription factor deletions of E. coli for efficient production of the polymer. This approach aimed at drawing out the latent potential of the host for efficient polymer production via indirect positive effects. Among 252 mutants from Keio Collection tested, eight mutants (ΔpdhR, ΔcspG, ΔyneJ, ΔchbR, ΔyiaU, ΔcreB, ΔygfI and ΔnanK) accumulated greater amount of polymer (6.2-10.1 g/L) compared to the parent strain E. coli BW25113 (5.1 g/L). The mutants increased polymer production per cell (1.1-1.5-fold) without significant change in cell density. The yield of the polymer from glucose was also higher for the selected mutants (0.34-0.38 g/g) than the parent strain (0.27 g/g). Therefore, the deletions of transcription factors should channel the carbon flux towards polymer production. It should be noted that the screening employed in this study identified beneficial mutants without analyzing causal relationship between the mutation and the enhanced polymer production. This approach, therefore, should be applicable to broad range of fermentation productions.