Fig. 5

Results and verification of the DoE on the impact of pH and temperature. T. reesei was cultivated in shake flasks on 70 g/L glucose as the sole carbon source and 80 mM urea as the nitrogen source for 96 h. A full factorial DoE with 2 levels was performed with temperatures 20 °C and 35 °C, and pH 3 and 6. Cultivations were performed in triplicates. Samples were taken every 24 h, and glucose and erythritol concentrations were determined by HPLC in the supernatants. Biomass was determined by dry cell weight measurement at the end of cultivation. The results were used to generate a model illustrated by RCPs for biomass (A.1), erythritol concentration (A.2), the ratio of erythritol concentration to biomass (A.3), and erythritol concentration to glucose consumed (A.4). The suggested extreme conditions (20 °C at pH 3 and 35 °C at pH 6 for 96 h of cultivation) and an additional condition (20 °C at pH 3 for 72 h followed by 24 h at 35 °C) were applied and the same parameters, namely biomass (B.1), erythritol concentration (B.2), the ratio erythritol concentration to biomass (B.3), and the ratio erythritol concentration to glucose consumed (B.4), were measured and calculated