Dialysis reactor operation

The influence of the OTR on kinetics (and therefore on productivity) was indicated in Equs. 5.169 and 5.170. Therefore, we will discuss here primarily those process engineering factors involved in various different types of reactors and operations. Last but not least, some unconventional reactors such as membrane (dialysis) reactors and synchronous culture techniques will be discussed. 

Figure 1. Proposed heparin circuit. The extracorporeal device could be a renal dialysis unit or a pump-oxygenator. The heparinase reactor could be part of a blood filter to be used either continuously (in which case heparin would, be added, continuously at the start of the circuit) or at the end of an operation. Heparin could thus be confined to the extracorporeal circuit.

Depending on the purity aind the history of the dry enzyme preparation, recovery yields of 90-100% expressed activity of the immobilized enzyme have been achieved. The activity of the soluble enzyme preparation after dialysis is approximately 400 IGIU/ ml and a 2X quantity of enzyme is utilized for immobilization with roughly 50% of the offered soluble enzyme being recovered after immobilization and 45-50% of the offered soluble enzyme resulting in expressed activity on the reactor when operated under the aibove conditions. Depending upon the activity of the purified enzyme, the activity of the carrier after immobilization is typically 600 IGIU/g. 

From the preceding analyses it is apparent that the behavior of reactor systems is more closely linked to the operation of the fermenter chamber than to operation of the reservoir. Therefore, the first step in designing a dialysis culture is to choose between the security and flexibility of batch cultures and the uniformity and economy of continuous techniques. 

Ultra and nanofiltration techniques based on dialysis in the reaction engineering of catalytic processes were originally developed for biotechnological applications, whereas their apphcation to organometalhc homogeneous catalysis has been a more recent development. Key contributions to the development of continuously operating membrane reactors for this type of catalytic systems are due to Kragl and others [23], while van Koten and van Leeuwen and their coworkers [24, 25] first reported the apphcation of this technique to dendrimer catalysis which led to its establishment in dendrimer chemistry. 

Figure L The microdialysis based glucose monitoring system with the silicon lamella structure operating as the enzyme reactor. The oxygen electrode monitored the changes in dissolved oxygen as the dialysis probe was immersed into samples of varying glucose concentrations.

Different sample pretreatment operations include dilution, membrane-extraction (gas diffusion, dialysis), liquid-phase extraction techniques (liquid/liquid extraction, liquid-phase microextraction, single-drop microextraction) and solid reactors and packed columns aiming to facilitate online chemical derivatization, chromatographic separation of target species, removal of interfering matrix compounds, enzymatic assays, or determination of trace levels of analyte via sorptive preconcentration procedures (Marshall et al., 2003 Economou, 2005 Miro and Hansen, 2006 Theodoridis et al., 2007 McKelvie, 2008 Ruzicka, 2014). In this context, BIA and the LOV configurations are particularly useful. Acid-base titrations can also be automated using simple SIA manifolds and potentiometric (van Staden et al., 2002) or photometric (Kozak et al., 2011) detection. Typically, a zone of the sample to be titrated is sandwiched between two zones of titrant by aspiration. In the case of photometric detection, an additional zone of a suitable pH-sensitive colored indicator is aspirated. The stacked zones are delivered to the detector and the width of the peaks is monitored and related to the pH of the solution. 

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