Dynamic control over feedback regulatory mechanisms improves NADPH flux and xylitol biosynthesis in engineered E. coli

• Published in: Metabolic engineering 2021-03, Vol.64, p.26-40
• Main Authors: Li, Shuai, Ye, Zhixia, Moreb, Eirik A., Hennigan, Jennifer N., Castellanos, Daniel Baez, Yang, Tian, Lynch, Michael D.
• Format: Article
• Language: English
• Subjects: BASIC BIOLOGICAL SCIENCES; Dynamic metabolic control; Metabolic dysregulation; NADPH; Xylitol
• ISSN: 1096-7176; 1096-7184
• DOI: 10.1016/j.ymben.2021.01.005

We report improved NADPH flux and xylitol biosynthesis in engineered E. coli. Xylitol is produced from xylose via an NADPH dependent reductase. We utilize 2-stage dynamic metabolic control to compare two approaches to optimize xylitol biosynthesis, a stoichiometric approach, wherein competitive fluxes are decreased, and a regulatory approach wherein the levels of key regulatory metabolites are reduced. The stoichiometric and regulatory approaches lead to a 20-fold and 90-fold improvement in xylitol production, respectively. Strains with reduced levels of enoyl-ACP reductase and glucose-6-phosphate dehydrogenase, led to altered metabolite pools resulting in the activation of the membrane bound transhydrogenase and an NADPH generation pathway, consisting of pyruvate ferredoxin oxidoreductase coupled with NADPH dependent ferredoxin reductase, leading to increased NADPH fluxes, despite a reduction in NADPH pools. These strains produced titers of 200 g/L of xylitol from xylose at 86% of theoretical yield in instrumented bioreactors. We expect dynamic control over the regulation of the membrane bound transhydrogenase as well as NADPH production through pyruvate ferredoxin oxidoreductase to broadly enable improved NADPH dependent bioconversions or production via NADPH dependent metabolic pathways. [Display omitted] •Decreases in NADPH pools lead to increased NADPH fluxes.•Pyruvate ferredoxin oxidoreductase coupled with NADPH-ferredoxin reductase improves NADPH production in vivo.•Dynamic reduction in acyl-ACP/CoA pools alleviate inhibition of membrane bound transhydrogenase and improve NADPH flux.•Xylitol titers >200 g/L in fed batch fermentations with xylose as a sole feedstock.