FIG. 1.

pH-stat-controlled hydrolysis of dPHB granules by purified PHB depolymerase PhaZ5. (A) Twenty-five milligrams of hypochlorite-purified dPHB granules was incubated in 15 ml of 1 mM Tris-HCl, pH 8.5, at 37°C. Three micrograms of purified PhaZ5 was added, as indicated by the arrow. The pH-stat unit was kept constant at pH 8.5, and the amount of NaOH necessary to keep the pH at 8.5 was recorded. (B) Dependence of (initial) hydrolysis rates (μmol NaOH consumed min⁻¹) on the amount of PhaZ5. Conditions were the same as described above for A, except that 5 mg dPHB granules was used. (C) Dependence of (initial) hydrolysis rates (μmol NaOH consumed min⁻¹) on the amount of PHB. Conditions were the same as those described above for A, except that the amount of PhaZ5 was 1 μg and the amount of dPHB granules was variable.