Fig. 4

Effect of various constant and non-constant H₂O₂ feeding rates on the saccharification of Avicel with Cellic^® CTec2. a, d The production of Glc4gemGlc, b, e the glucan conversion and c, f the concentration of AscA. Unless otherwise stated, reactions were carried out with 10% (w/w) DM of Avicel, 4 mg/g DM of Cellic^® CTec2 and 1 mM of AscA, in 50 mM sodium acetate buffer at pH 5.0 and 50 °C, with constant supply of H₂O₂ (600 µL h⁻¹). To ensure anaerobic conditions, all reactions were carried out with constant sparging of nitrogen at a flow rate of 100 mL min⁻¹, with the exception of the aerobic control reactions (O₂ and O ^a₂ ), which were sparged with air at the same flow rate. “N₂” stands for the anaerobic control reaction. All three control reactions were run without the addition of H₂O₂. “O ^a₂ ” was run in the absence of AscA. Repeated additions of AscA to a final concentration of 1 mM in the reactions fed at 300 and 600 µM h⁻¹ are marked with an asterisk (*). For the experiment called “Decrease”, the H₂O₂ feed rate was gradually lowered as follows: 300 µM h⁻¹ from 0 to 6 h; 200 µM h⁻¹ from 6 to 12 h; 100 µM h⁻¹ from 12 to 24 h and 50 µM h⁻¹ from 24 to 48 h. For the experiment called “Addition”, the H₂O₂ feed rate was as follows: 0 µM h⁻¹ from 0 to 24 h and 300 µM h⁻¹ from 24 to 48 h. Error bars for glucan conversion represent standard deviations for two technical replicates. The decrease of Glc4gemGlc over time that is observed in some of the reactions (a, d) is due to a first order degradation process that is independent of the presence of AscA and H₂O₂; see main text for details