Fig. 4

Temperature stability of crude inulosucrase. The remaining total activity of crude inulosucrase after incubation at 40 °C, 45 °C, or 50 °C was determined every 24 h for 4 days and compared to the initial activity. Crude inulosucrase was diluted in 1 ml 25 mM sodium acetate buffer (pH 5.5) to a volume activity of 667 U, sterile filtered, and incubated at 40 °C, 45 °C, or 50 °C for 4 days. Samples (6 µl) were taken and activity assays were performed in biological duplicates at 40 °C in 1 mL assays containing 570 g L⁻¹ sucrose, 25 mM sodium acetate buffer (pH 5.5), and 1 mM CaCl₂. Samples were taken at regular intervals within 30 min. The increase in glucose concentration, which represents inulosucrase total activity (hydrolysis and transfructosylation), was evaluated by individual GOPOD assays (Megazyme Inc.)