Fig. 8.

Influence of polygalacturonic acid pulses on the cultivation of U. maydis AB33P5ΔR/AtPgaX. The strain was grown on glucose (6.5 g/L) and polygalacturonic acid (10 g/L) as carbon sources. Pulses of polygalacturonic acid were added at indicated time points (arrows). At 68.5 h, all cultures except the reference received a second substrate pulse. The values for the oxygen transfer rate (OTR), the overall oxygen consumption (OT) and the predicted residual polygalacturonic acid concentration (PolyGalA_calc) refer to the initial filling volume. The vertical dashed line represents the beginning of polygalacturonic acid consumption. a Mean value of biological duplicates of the OTR. b Mean value of biological duplicates of RQ. The dotted horizontal line represents RQ = 1. For clarity, the RQ is only shown for OTR > 2 mmol/L/h. c Mean value of duplicates of the OT. d PolyGalA_calc according to Eq. (6). The RQ drops below 1 during consumption of polygalacturonic acid, indicating depletion of accessible substrate. Thus, the line for PolyGalA_calc in Fig. 8d is dotted during that time. The mean values of biological duplicates are shown for better clarity. Culture conditions: modified Verduyn medium, 0.2 M MOPS, initial pH 6.5, 250 mL flask, initial filling volume 20 mL, shaking frequency 300 rpm, shaking diameter 50 mm, initial OD₆₀₀ = 0.2, temperature 30 °C. The mass of polygalacturonic acid in one pulse equals the initial mass supplemented in the medium. Pulses of 5 mL polygalacturonic acid solution (40 g/L) were added