Reactors cells

However, there are disadvantages to using immobilised cells. The cell may contain numerous catalytically active enzymes, which may catalyse unwanted side reactions. Also, the cell membrane itself may serve as a diffusion barrier, and may reduce productivity. The matrix may sharply reduce productivity if the microorganism is sensitive to product inhibition. One of the disadvantages of immobilised cell reactors is that the physiological state of the microorganism cannot be controlled. 

The immobilised cell reactor (ICR) experiments were undertaken to determine the performance of immobilised Propionibacterium acidipropionici in a plug-flow tubular reactor. The... 

CASE STUDY ETHANOL FERMENTATION IN AN IMMOBILISED CELL REACTOR USING SACCHAROMYCES CEREVISIAE... 

Fermentation of sugar by Saccharomyces cerevisiae, for production of ethanol in an immobilised cell reactor (ICR), was successfully carried out to improve the performance of the... 

Keywords immobilised cell reactor (ICR) Saccharomyces cerevisiae ethanol fermentation encapsulated beads calcium alginate... 

Use of biofilm reactors for ethanol production has been investigated to improve the economics and performance of fermentation processes.8 Immobilisation of microbial cells for fermentation has been developed to eliminate inhibition caused by high concentrations of substrate and product, also to enhance productivity and yield of ethanol. Recent work on ethanol production in an immobilised cell reactor (ICR) showed that production of ethanol using Zymomonas mobilis was doubled.9 The immobilised recombinant Z. mobilis was also successfully used with high concentrations of sugar (12%-15%).10... 

Fig. 8.13. Glucose concentration and ethanol production versus retention time in immobilised cell reactor with initial substrate concentration of 150 g l1 glucose. Reprinted from Najafpour et al. (2004).18 Copyright with permission from Elsevier.

Najafpour, G.D., Younesi, H. and Ku Ismail, K.S., Ethanol Fermentation in Immobilized Cell Reactor (ICR) Using Saccharomyces cerevisiae , Bioresource Technology, vol. 92/3, 2004, pp. 251-260. 

Thus a lineal- relation between In (CA/CA0) and the reactor length should exist if the model accurately describes the immobilised cell reactor. The experimental data fitting the model was discussed earlier. 

Figure 9.23. Schematic diagram of the apparatus (a, left) and of the electrochemical cell-reactor (b, right) used for H2 oxidation on Pt/Nafion.35 Reproduced by permission of The Electrochemical Society, Inc.

Two types of continuous flow solid oxide cell reactors are typically used in electrochemical promotion experiments. The single chamber reactor depicted in Fig. B.l is made of a quartz tube closed at one end. The open end of the tube is mounted on a stainless steel cap, which has provisions for the introduction of reactants and removal of products as well as for the insertion of a thermocouple and connecting wires to the electrodes of the cell. A solid electrolyte disk, with three porous electrodes deposited on it, is appropriately clamped inside the reactor. Au wires are normally used to connect the catalyst-working electrode as well as the two Au auxiliary electrodes with the external circuit. These wires are mechanically pressed onto the corresponding electrodes, using an appropriate ceramic holder. A thermocouple, inserted in a closed-end quartz tube is used to measure the temperature of the solid electrolyte pellet. 

Air monitoring will be required, e.g., when volatiles are handled in quantity, where use of radioactive isotopes has led to unacceptable workplace contamination, when processing plutonium or other transuranic elements, when handling unsealed sources in hospitals in therapeutic amounts, and in the use of hot cells/reactors and critical facilities. Routine monitoring of skin, notably the hands, may be required. 

Laboratory reactors for studying gas-liquid processes can be classified as (1) reactors for which the hydrodynamics is well known or can easily be determined, i.e. reactors for which the interfacial area, a, and mass-transfer coefficients, ki and kc, are known (e.g. the laminar jet reactor, wetted wall-column, and rotating drum, see Fig. 5.4-21), and (2) those with a well-defined interfacial area and ill-determined hydrodynamics (e.g. the stirred-cell reactor, see Fig. 5.4-22). Reactors of these two types can be successfully used for studying intrinsic kinetics of gas-liquid processes. They can also be used for studying liquid-liquid and liquid-solid processes. 

Tan et al. [29] demonstrated the use of a plug flow reactor of immobilized Lactobacillus kefiri cells for the synthesis of the intermediate (5I )-hydroxyhexane-2-one. This immobilized-cell reactor operated at a maximum conversion yield of 100% and a selectivity of 95%. The production of (5/ )-hydroxyhexane-2-one was extended to an operation time of 6 days. During this time (91 residence times), a space-time yield of 87gL xday 1 and a productivity of 07 8 gwet cell weight 1 were obtained. 

The use of immobilized cell reactors have shown improved biocatalyst stability, however, the specific rates of desulfurization have been much lower than for suspended cell (stirred) reactors. Mass transfer limitations have been significant resulting in lower rates. Thus, the activity is sacrificed to achieve stability. Further work in this area and improved immobilization matrices can help improve the activity along with the stability. 

Demonstrations of the scale-up, development, and integration of hardware with real materials of construction must focus on the robustness of the parallel flow in multiple-cell reactors. The issues of cell blockage, hydrocyclone performance, and NOx reformer performance must be addressed. 

Figure 12.10 Examples of structured catalytic reactors for kinetic measurements (a) annular reactor [47, 61] (b) plate cell reactor [75].

The view-cell reactor is made of titanium and has two sapphire windows, a gas inlet valve and an outlet valve, as shown in Figure 3. The view cell is interfaced with a pressure transducer, a thermocouple, and a pressure relief valve. The pressure and temperature are computer-monitored during the reaction. 0.6 ml of 50 wt% H2O2/H2O (10.41 mmoles), 0.20ml of pyridine (2.47 mmoles), or some other base, was dissolved in 5 ml of acetonitrile or methanol, and was added to the reactor. 2.2 ml of supercritical CO2 was charged after lOOmg of propylene (2.38 mmoles) had been added to the reactor. The reactor was heated with a band heater at 40 - 70°C for 3, 6, 12, and 24 hr reaction periods. Following a batch conversion experiment, the amounts of products formed were determined by GC and GC/MS. 

Figure 3. The view-cell reactor and diagram of system Acknowledgements...

Caloz, F F. F. Fenter, K. D. Tabor, and M. J. Rossi, I Design and Construction of a Knudsen-Cell Reactor for the Study of Heterogeneous Reactions over the Temperature Range 130-750 K, Performances and Limitations, Rev. Sci. Instrum., 68, 3172-3179 (1997). 

The regioselective course of the Diels-Alder reaction in supercritical carbon dioxide was investigated. The analysis failed to confirm the previously reported dramatic effect of reaction conditions on Diels-Alder regiochemistry. The results highlighted the importance of verifying phase behavior when sampling CO2 reaction mixtures and the utility of a view-cell reactor that allows direct monitoring of phase behavior (Ren-slo et al., 1997). 

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