This standard curve showed the correlation between the PHB concentrations (X axis) and the ratios between peak areas of crotonic acid (PHB-hydrolyzed product) to adipic acid (Y axis) at R2 = 0.996 indicating their absolute linear correlation. The HPLC analysis showed that the PHB content of Calothrix Scytonemicola TISTR 8095 is 25.20% weight to cell dry weight (w cdw-1). This HPLC analysis was used to determine the PHB contents in 135 strains grown under six culture conditions.