One of the cornerstones of the 'Bioeconomy' will rest on our ability to exploit renewable carbon resources to produce environmental eco-friendly fuels and chemicals that will profitably replace those derived at present from fossil resources. The POLYDHB project is in frame with this endeavour. This project originality stands on previous works carried out by two partners of this proposal which have exploited synthetic biology toolbox combined to metabolic and enzymes engineering to construct a synthetic pathway that leads to the microbial production of a non-naturally metabolite 2,4-dihydroxybutyric acid (DHB) from renewable carbon sources (i.e. sugars). Initially conceived as a precursor for the synthesis of the methionine to target the field of animal nutrition, this molecule actually turns out to be a unique ‘green’ platform chemical for the production of other bio-based products with application in chemical and pharmaceutical industries. The purpose of the POLYDHB project is here to demonstrate that DHB can be used as an original non-natural monomer for the production of new bio-sourced and biodegradable polymers. The scientific and technical challenges of this project will be realized through three workpackages: (I) production of pure enantiomers and lactide /lactone derived from DHB, (II) development of a chemocatalytic process of (co)polymerisation of DHB and/or its lactone and lactide derivatives alone or with other monomers, and (III) conception of a microbial process for the synthesis of DHB-based polymers. In each of these workpackages, scientific risks have been identified and contingency solutions clearly proposed. To succeed in this objective, a multidisciplinary and complementary core of expert in the field of Systems and Synthetic Biology (LISBP, Toulouse), Polymer Chemistry (LCPO, Bordeaux) with the participation of a Japanese team expert in molecular biology of bio-sourced polymers has been set-up. Moreover, the strong commitment of the industrial partner Adisseo in this project is not solely justified by its indispensable position in mastering the chemical and microbial process for DHB production, but it is also an asset for the industrial exploitation of this molecule on markets other than nutrition animal that can be opened from the results obtained in this project. The ambition of POLYDHB project is to reach the technology readiness level of 4 within the 3 years period.