Optimized production of polyhydroxyalkanoates from Priestia megaterium using sugar beet molasses: a cost-effective...

Polyhydroxyalkanoates (PHAs), eco-friendly microbial bioplastics, have the potential to replace synthetic plastics, reducing pollution. The novelty of this study lies in the integration of cost‑effective substrate utilization, systematic optimization, and preliminary evaluation of multifunctional properties of PHA. Therefore, this study assessed 29 bacterial isolates for PHA production utilizing sugar beet molasses (SBM) as an inexpensive carbon source. Among the tested isolates, the strain SNS1 exhibited the highest PHA production and was genetically identified as Priestia megaterium. An optimization process and a Plackett-Burman design were applied to determine the conditions for maximum PHA production in shaking flasks. As a result, PHA concentration reached 4.79 g/L on 6% SBM, 0.50 g/L ammonium oxalate, pH 8.50, 37 °C, 200 rpm, and a 24 h incubation period. The biosynthesized PHAs were identified as Poly(3-hydroxybutyrate) (P3HB) using 1H-NMR, 13C-NMR, FTIR spectroscopy, and GC-MS. Thermal properties, evaluated by DSC and TGA analyses, indicated the presence of pure P3HB. The purified PHA sheet was tested for ultraviolet (UV) protection, showing potential as a sun protectant with an UV-shielding factor of 15.23, providing 35% UV light absorption. This work demonstrates the potential of Priestia megaterium for cost-effective and efficient PHA production with desirable polymer properties.