Production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) co-polymer by the diazotrophic cyanobacterium Aulosira fertilissima CCC 444

Accumulation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate), P(3HB-co-3HV), a well-known co-polymer of polyhydroxyalkanoates family, was investigated in a N₂-fixing cyanobacterium, Aulosira fertilissima CCC 444, in presence of propionate and valerate in the culture medium. The most significant rise in P(3HB-co-3HV) co-polymer content up to 77 % of dry cell weight was recorded under 0.5 % fructose?+?0.4 % valerate supplementation depicting a productivity of 38 mg L^?1 day^?1, which was further increased by 2.5-fold, i.e., up to 95 mg L^?1 day^?1 under P deficiency. Surface analysis revealed a regular and smooth surface for P(3HB-co-3HV) co-polymer, against rugged and porous surface of the homopolymer of poly-β-hydroxybutyrate. X-ray diffraction showed semi-crystalline nature of the P(3HB-co-3HV) co-polymer. The thermal and mechanical properties of the co-polymer are comparable with the chemoheterotrophic bacterial polymers, thus opens up possibilities of using cyanobacterial PHAs in various fields.