Poly-3-hydroxy butyrate production and it's characterization from a new species, Rhodobacter alkalitolerans strain JA916T in different growth conditions

Rhodobacter alkalitolerans strain JA916T (R. alkalitolerans) is a purple non‑sulfur photosynthetic bacterium that grows in alkaline conditions. It is metabolically versatile, and can produce polyhydroxy butyrate (PHB) as internal storage carbon. We observed higher expression of PHB-synthesizing genes and greater PHB production under normal pH (npH) conditions compared to high pH (hpH), along with increased biomass production. The purity of PHB was analyzed using fourier transformed infrared spectroscopy, gas chromatography-mass spectrometry, and proton and carbon nuclear magnetic resonance, confirming it as a polymer of 3-hydroxybutric acid. Furthermore, PHB was characterized using differential scanning calorimetry and thermogravimetric analysis, revealing a melting temperature (T_m) of 177.59 °C and the highest degradation rate at 282.02 °C. This is the first report of high-yield PHB production within 24-28 h of high light exposure to R. alkalitolerans, highlighting its potential as a biodegradable plastic alternative.