*2.2. Experimental Set-Up*

Figure 2 shows the two serially arranged bioreactors used to conduct the experiments. The reactors were two 8 L Acetators from Heinrich Frings GmbH & Co. KG (Rheinbach, Germany) equipped with self-aspirating turbines in the bottom in order to obtain a dispersion of fine air bubbles. The reactors were highly efficient in transferring oxygen between the gas phase and the substrate [11]. The ensemble was interfaced to a computer for automated operation, especially with regards to loading and unloading of reactors, and monitoring of the process. This resulted in highly reproducible loading and unloading, and in efficient acquisition of data [6,11,37].

**Figure 2.** The experimental set-up for the bioconversion of ethanol into acetic acid.
