Methanol-induced chain termination in poly(3-hydroxybutyrate) biopolymers: Molecular weight control

Revealing the Phenotypic and Genomic Background for PHA Production from Rapeseed-Biodiesel Crude Glycerol Using Photobacterium ganghwense C2.2

Polyhydroxyalkanoates (PHA) are promising biodegradable and biocompatible bioplastics, and extensive knowledge of the employed bacterial strain's metabolic capabilities is necessary in choosing economically feasible production conditions. This study aimed to create an in-depth view of the utilization of Photobacterium ganghwense C2.2 for PHA production by linking a wide array of characterization methods: metabolic pathway annotation from the strain's complete genome, high-throughput phenotypic tests, and biomass analyses through plate-based assays and flask and bioreactor cultivations. We confirmed, in PHA production conditions, urea catabolization, fatty acid degradation and synthesis, and high pH variation and osmotic stress tolerance. With urea as a nitrogen source, pure and rapeseed-biodiesel crude glycerol were analyzed comparatively as carbon sources for fermentation at 20 °C. Flask cultivations yielded 2.2 g/L and 2 g/L PHA at 120 h, respectively, with molecular weights of 428,629 g/mol and 81,515 g/mol. Bioreactor batch cultivation doubled biomass accumulation (10 g/L and 13.2 g/L) in 48 h, with a PHA productivity of 0.133 g/(L·h) and 0.05 g/(L·h). Thus, phenotypic and genomic analyses determined the successful use of Photobacterium ganghwense C2.2 for PHA production using urea and crude glycerol and 20 g/L NaCl, without pH adjustment, providing the basis for a viable fermentation process.

The 'PHAome'

Polyhydroxyalkanoates (PHAs) are a family of polyesters synthesized by bacteria. Similarly to the genome, transcriptome, and proteome (the entire array of nucleic acids and proteins present in a cell or population of cells at a given time), the PHA spectrum exhibits diverse and dynamic modifications - the 'PHAome' - reflecting not only by the diversity of monomers, homopolymers, random and block copolymers, functional and graft polymers, molecular weights, and combinations of the above, but also the ranges of PHAs with various molecular weights and monomer ratios that are present at a particular timepoint in a bacterial cell. Echoing the Materials Genome Initiative (MGI) launched in 2011 to develop an infrastructure to accelerate advanced materials discovery and deployment, understanding the PHAome and ensuring an ample supply of PHAs based on it will promote the discovery of new properties and applications of this family of advanced materials.