Determination of poly-β-hydroxybutyric acid in Bacillus thuringiensis by capillary zone electrophoresis with indirect ultraviolet absorbance detection

A new capillary electrophoresis method for determining poly-β-hydroxybutyric acid (PHB) in Bacillus thuringiensis was established. Poly-β-hydroxybutyric acid in samples was hydrolyzed by sulphuric acid and neutralized by Ba(OH)2. The content of produced β-hydroxybutyrate was then determined by capillary zone electrophoresis (CZE) with indirect UV detection at 254 nm. With 5 mM p-hydroxybenzoate and 0.5 mM tetradecyltrimethylammonium bromide (TTAB) at pH 8.0 as carrier electrolyte, β-hydroxybutyrate can be determined within 6 min. Standard regression equation was made by β-hydroxybutyrate, and the linear range was 2–1000 μg/ml. The relative standard deviations (RSDs) for migration time and peak area are both less than 1.0%. The detection limit for β-hydroxybutyrate was 0.2 μg/ml, which is two to three orders of magnitude lower than that of the gas chromatography (GC) method. The capillary electrophoresis method was successfully applied to determine poly-β-hydroxybutyric acid in fermentation broth and single colony. The added standard recovery was 96%.