Fluorescence intensities of PHB powder and intracellular PHB granules. To exam the correlation between PHB concentration and fluorescence intensity, different concentrations of aqueous PHB suspension were incubated with 2 µg/mL LipidGreen1 for 30 min, and then the fluorescence intensities were measured at 450 nm excitation and 510 nm emission wavelengths, respectively (a). On the other hands, intracellular PHB contents were measured by collecting PHB-producing cells every 2 or 3 h during cultivation. The fluorescence intensities were measured with 2.0 µg/ml of LipidGreen1 (b) and Nile red (c). The PHB contents of the cells at different times were analyzed by GC. The solid line indicates the regression line.