Isolation and optimization of poly β hydroxybutyrate producing cyanobacterial strains.

ABSTRACT

Cyanobacteria have many unexploited potential for natural products with a huge variability in structure and biological activity. Under stress conditions they are reported to produce biopolymers like poly-β-hydroxybutyrate (PHB), which can be produced intracellularly.Cyanobacteria are capable of synthesizing small amount of poly-β-hydroxybutyrate (PHB) under nitrogen and phosphorous starvation conditions. High performance liquid chromatography (HPLC) analysis revealed that about percentage PHB of the cell dry weight (CDW) was accumulated under mixotrophic culture condition. However, Nile red stained cells showed the presence of large quantities of granules in the cell cytoplasm when viewed under fluorescent microscope. The qualitative observation was in contrast to the quantitative HPLC analysis which suggested that the fluorescent granules are PHB. Among the ten different isolates, three strains showed the accumulation of PHB. The amount of PHB produced after 10 days in the depleted conditions are 1.182 mg/l for spirulina, 2.322 mg/l for anabena and 3.741 mg/l. The maximum PHB producer was further studied in detail. The extracted polymer was compared with the authentic PHB and was confirmed to be PHB using FTIR analysis. The present study shows increased PHB accumulation in different species by nitrogen and phosphorous depleted condition and pH concentration in the growth media.