Aulosira culture supplemented with 0.5% citrate
under P deficiency followed by 5 days of dark incubation
also depicted a PHB accumulation of 51% (dcw).
PHB
content of A. fertilissima reached up to 77% (dcw) under P
deficiency with 0.5% acetate supplementation. Optimization
of process parameters by response surface methodology
resulted into polymer accumulation up to 85% (dcw) at
0.26% citrate, 0.28% acetate, and 5.58 mg L−1 K2HPO4 for
an incubation period of 5 days. In the A. fertilissima cultures
pre-grown in fructose (1.0%)-supplemented BG 11 medium,
when subjected to the optimized condition, the PHB pool
boosted up to 1.59 g L−1, a value ∼50-fold higher than the
control. A. fertilissima is the first cyanobacterium where PHB
accumulation reached up to 85% (dcw) by manipulating the
nutrient status of the culture medium. The polymer extracted
from A. fertilissima exhibited comparable material properties
with the commercial polymer. As compared with heterotrophic
bacteria, carbon requirement in A. fertilissima for PHB
production is lower by one order magnitude; thus, low-cost
PHB production can be envisaged