Use of Sensors in a Scale-Down Simulator

Abstract

amilton's VisiFerm Arc 120 dissolved oxygen and Polilyte Plus Arc 120 pH sensors are valuable tools when used in a plug flow reactor (PFR) to measure the metabolic response of Bacillus subtilis to oxygen availability. The PFR is connected to a common stirred tank reactor (STR) to simulate conditions in large-scale industrial processes. The impact of inhomogeneities of oxygen, and potentially pH, on Bacillus subtilis cultivations were observed. This study leads to the determination that such inhomogeneities will also exist, and can be measured and corrected, in industrial processes. HTo achieve conditions that mimic those in large scale, determination of the hydrodynamic behavior by ascertaining the residence time distribution is of basic interest. Therefore, a reliable measurement of the pH along the PFR is necessary.During cultivation, the distribution of oxygen and pH along the PFR allows an exact description of the process conditions and enables the user to adopt them to large-scale conditions. The PFR is characterized by high inhomogeneities in the axial direction with respect to oxygen concentration. Since oxygen limitation in industrial fedbatch processes occurs near the feed line, the feed is introduced at the entrance of the PFR. Unlike the first lab-scale two-compartment reactors, the system in this study is equipped with five pH and optical dissolved oxygen (DO) sensors along the height of the PFR (Figure 1).