Biopolymer polyhydroxyalkanoate production from Arthrospira platensis NLHT3 cyanobacterium isolated in Vietnam

Cyanobacteria are photosynthesis microorganisms that can convert CO₂ into biomass using light as an energy source. Cyanobacteria can also produce polyhydroxyalkanoates (PHA) for intracellular energy and carbon storage, especially under nutrient-deficient conditions. This study investigates the effects of nutrient media and culturing conditions on PHA accumulation in Arthrospira platensis NLHT3. PHA accumulation in A. platensis NLHT3 reached the optimum value of 28.2 % on the day 15 of cultivation with supplemented mixture of 0.1 M of NaHCO₃ and 94 mM of C₃H₅NaO₂ (sodium propionate) as carbon sources, 12 mM of NaNO₃ as nitrogen source, and 1.72 mM of K₂HPO₄ as phosphorous source. An even higher PHA accumulation of 39 % was achieved when light intensity increased from 75 to 108 µmol photons m⁻² s⁻¹ at light/dark cycle of 16 h/8 h and the abovementioned carbon and nutrient concentrations. The accumulated PHA was identified as poly(3-hydroxybutyrate) (PHB) using Fourier-transform infrared spectroscopy and ¹H and ¹³C nuclear magnetic resonance. The results reported here reveal the great potential of A. platensis NLHT3 for large-scale production of biodegradable PHA plastics.