Ex-cell processes

Fig. 2. Flow diagram of an indirect electrochemical process with external regeneration of the redox catalyst (ex-cell process)...

The action of the transient reagent was tested on amides (ex-cell process) to point out the formation in high yields of oxazolidinediones [278]. 

Economics encourage the simpler in-cell mode. The ex-cell mode is advantageous because the electrode reaction and chemical step can be optimized separately. The electrolyte can be purified/conditioned between the reactor and the cell. Sn(II) is used as mediator for the reduction of nitro tegretol [125,126] in 6 M HCl/ethanol. The Sn(IV) formed is reduced eleetrochemically after stripping off the alcohol, either to the Sn(II) state using a percolated Sn electrode or to the tin metal on a rotated carbon electrode. The reduction to the metal has the advantage that the mediator can be purified/washed before being recycled to the process [126],... 

Development of serum-free medium has great value for large-scale biopesticide production. The latest formulations are serum-free, such as SF900II (GIBCO /Invitrogen) and EX-CELL (JRH Biosciences). Cell culture medium supplementation using yeast extract (usually from alcoholic fermentation processes), milk, or soy protein concentrates, can also be an alternative to decrease cell culture medium costs (more details can be found in Chapter 5). 

Due to recent trends in cellular therapy, the pharmaceutical companies have put emphasis on the use of ex vivo electroporation for both DNA and dmg delivery. Using the flow thm system, employing a pump that moves the cell suspension through an electroporation chamber where cells are porated. The entire operation is aimed to a closed system to minimize contamination and facilitate commercial scale cell-processing operations. 

The indirect, ex-cell chromic acid oxidation is the oldest industrial organic electrochemical process. 

C Comninellis. The Industrial Application of the Indirect ex-cell Oxidation Process. 5th European Conf on Electrochem Processing, Chester. ICI, EA-Technology, eds. April 12-16, 1998. 

Ex-cell-mediated oxidation has similarities and differences with respect to the indirect electrochemical oxidation known in this field. The principal similarity is that both methods use an active oxidant that oxidizes the organic species, i.e., both methods assure the proximity of active oxidant-organic species then, oxidation occurs efficiently even when the concentration of the organic species is low. The principal difference concerns the control of the operating conditions of the steps that compose the mediated oxidation occurring in these cases. In indirect oxidation, the steps of precursor production, mixing, activation, and oxidation occur in the electrochemical cell, where even direct oxidation can occur. In ex-ceU-mediated oxidation, a specific piece of equipment is dedicated at every step of the process, and the control of each step allows its efficient realization. 

Ex-cell, i.e. the chemical reaction is carried out in a reactor separate to the cell. This approach has the advantages that the conditions for the electrode reaction and the chemical step may be optimized separately and also that the electrolyte may be conditioned/purified between the reactor and the cell. On the other hand, more unit processes are necessary and economic driving forces will encourage the process designer to combine the cell and reactor as closely as possible. 

L-Phenylalanine can be synthesised from trims-cinnamic add (Figure A8.12) catalysed by a L-phenylalanine ammonia-lyase from Rhodococcus glutinis. The commercialisation of the process was limited by the low conversion (70%), low stability of the biocatalyst and die severe inhibition exerted by trims-cinnamic add. These problems were largely overcome by researchers at Genex. The process, commercialised for a short period by Gen ex, involves a cell-free preparation of phenylalanine-ammonia-lyase activity from Rhodotorula rubra. 

The initial approach to gene therapy involved manipulation of gene expression ex vivo. Toward this end, the desired target cells are identified and subsequently removed from the subject, transfected in vitro, then reintroduced into the patient. A number of protocols have been established for the ex vivo transfection of a wide variety of cell types. This method allows specific cell targeting and high transfection efficiency. However, the process is time consuming, complex, and costly. Additionally, the method is not applicable to all situations, such as those in which an immediate modification is required. 

Biological effects of SODs are widely studied in many in vitro, ex vivo, and in vivo experiments many of these studies have already been considered throughout this book. Examples of SOD application for the treatment of free radical pathologies are discussed in Chapter 31. Some studies related to the effects of SODs on free radical processes in cells and tissues are discussed below. 

Under the diffusive laminar flow conditions, the ability to add reagents at specific locations or times leads to the unique ability to control and monitor the spatial and temporal domain of dynamic chemical processes. This attribute has some analogies with the control exerted on biochemical reactions by the micron-scale structures of living cells. Ex-... 

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