Maltose Utilization as a Novel Selection Strategy for Continuous Evolution of Microbes with Enhanced Metabolite Production

5 years ago

Maltose Utilization as a Novel Selection Strategy for Continuous Evolution of Microbes with Enhanced Metabolite Production

Yi-Nan Wu, Chong Zhang, Xin-Hui Xing, Tian-Min Wang, Shu-De Liu

We have developed a novel selection circuit based on carbon source utilization that establishes and sustains growth–production coupling over several generations in a medium with maltose as the sole carbon source. In contrast to traditional antibiotic resistance-based circuits, we first proved that coupling of cell fitness to metabolite production by our circuit was more robust with a much lower escape risk even after many rounds of selection. We then applied the selection circuit to the optimization of L-tryptophan (l-Trp) production. We demonstrated that it enriched for specific mutants with increased l-Trp productivity regardless of whether it was applied to a small and defined mutational library or a relatively large and undefined one. From the latter, we identified four novel mutations with enhanced l-Trp output. Finally, we used it to select for several high l-Trp producers with randomly generated genome-wide mutations and obtained strains with up to 65% increased l-Trp production. This selection circuit provides new perspectives for the optimization of microbial cell factories for diverse metabolite production and the discovery of novel genotype–phenotype associations at the single-gene and whole-genome levels.

Publisher URL: http://dx.doi.org/10.1021/acssynbio.7b00247

DOI: 10.1021/acssynbio.7b00247