Abstract
In this work, we describe the construction of a synthetic metabolic pathway enabling direct biosynthesis of 1,3-propanediol (PDO) from glucose via the Krebs cycle intermediate malate. This non-natural pathway extends a previously published synthetic pathway for the synthesis of (L)-2,4-dihydroxybutyrate (L-DHB) from malate by three additional reaction steps catalyzed respectively, by a DHB dehydrogenase, a 2-keto-4-hydroxybutyrate (OHB) dehydrogenase and a PDO oxidoreductase. Screening and structure-guided protein engineering provided a (L)-DHB dehydrogenase from the membrane-associated (L)-lactate dehydrogenase of E. coli and OHB decarboxylase variants derived from the branched-chain keto-acid decarboxylase encoded by kdcA from Lactococcus lactis or pyruvate decarboxylase from Zymomonas mobilis. The simultaneous overexpression of the genes encoding these enzymes together with the endogenous ydhD-encoded aldehyde reductase enabled PDO biosynthesis from (L)-DHB. While the simultaneous expression of the six enzymatic activities in a single engineered E. coli strain resulted in a low production of 0.1 mM PDO from 110 mM glucose, a 40-fold increased PDO titer was obtained by co-cultivation of an E. coli strain expressing the malate-DHB pathway with another strain harboring the DHB-to-PDO pathway.
Highlights
A central goal of the bioeconomy consists in reducing our dependence on petroleum by focusing on the development of efficient, sustainable and eco-friendly processes for production of bio-based chemicals and fuels1,2. 1,3-Propanediol (PDO) is an important commodity chemical that can serve as a precursor monomer for the synthesis of industrially relevant polymers, including polyesters, polyethers and polyurethanes
We designed and experimentally validated a de novo metabolic pathway leading to the production of (L)-DHB from glucose via malate by expressing malate kinase, malate semialdehyde dehydrogenase and malate semialdehyde reductase enzyme activities in E. coli[19]
We explored the feasibility of a synthetic pathway enabling PDO biosynthesis from glucose under aerobic conditions via the Krebs cycle intermediate (L)-malate, which is based on the extension of a previously published (L)-DHB metabolic pathway[19]
Summary
A central goal of the bioeconomy consists in reducing our dependence on petroleum by focusing on the development of efficient, sustainable and eco-friendly processes for production of bio-based chemicals and fuels1,2. 1,3-Propanediol (PDO) is an important commodity chemical that can serve as a precursor monomer for the synthesis of industrially relevant polymers, including polyesters, polyethers and polyurethanes. While no natural microorganisms have been found to directly convert sugars to PDO, the adoption of two-stage and co-fermentation processes was shown to enable a better control of cultivation conditions and a wider flexibility in terms of substrate utilization[5,9,10] Another approach is the engineering of microorganisms for the direct production of PDO from sugars via glycerol, which led Genencor and DuPont to develop a fermentation process employing a genetically modified E. coli strain able to produce PDO aerobically at high titer and yield[11].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
