Fig. 8
Two-stage process for the degradation of benzoate (brown diamond) and 4HB (blue up pointing triangle) in a mixture with glucose (yellow circle) and the subsequent conversion to ethanol (blue square). The total bacterial + yeast OD (dark green circle). ACN2090 and ACN2091 were inoculated into a mixture of 100 g/L glucose, 5 mM 4HB, and 2.5 mM benzoate. After 9.7 h, both aromatic carbon sources were depleted, and a feed of 100 g/L glucose, 11 mM 4HB, and 6 mM benzoate was introduced at a constant flowrate of 1 mL/min (an initial dilution rate of 0.06 h−1), resulting in an increase of the bioreactor volume to approximately 1.6 L after an additional 9.8 h. After this feed was terminated, the temperature was raised to 55 °C and the pH lowered to 4.3, and then, the temperature quickly lowered to 42 °C and the pH increased to 5.2 (the complete cycle required 3.5 h). After inoculation with K. marxianus, aerobic conditions were provided for 9.3 h before switching to anaerobic conditions for the final 17.5 h