Tailored polyhydroxyalkanoate production from renewable non-fatty acid carbon sources using engineered Cupriavidus necator H16

Abstract

As thermoplastic, nontoxic, and biocompatible polyesters, polyhydroxyalkanoates (PHAs) are considered promising biodegradable plastic candidates for diverse applications. Short-chain-length/medium-chain-length (SCL/MCL) PHA copolymers are flexible and versatile PHAs that are typically produced from fatty acids, which are expensive and toxic. Therefore, to achieve the sustainable biosynthesis of SCL/MCL-PHAs from renewable non-fatty acid carbon sources (e.g., sugar or CO₂), we used the lithoautotrophic bacterium Cupriavidus necator H16 as a microbial platform. Specifically, we synthesized tailored PHA copolymers with varying MCL-3-hydroxyalkanoate (3HA) compositions (10-70 mol%) from fructose by rewiring the MCL-3HA biosynthetic pathways, including (i) the thioesterase-mediated free fatty acid biosynthetic pathway coupled with the beta-oxidation cycle and (ii) the hydroxyacyl transferase-mediated fatty acid de novo biosynthetic pathway. In addition to sugar-based feedstocks, engineered strains are also promising platforms for the lithoautotrophic production of SCL/MCL-PHAs from CO₂. The set of engineered C. necator strains developed in this study provides greater opportunities to produce customized polymers with controllable monomer compositions from renewable resources.

Keywords: Biodegradable polymer; Metabolic engineering; Polyhydroxyalkanoate; Renewable source; Short-chain-length/medium-chain-length PHA copolymer (SCL/MCL-PHA).