Membrane bioreactor features

Equation (10.2) applies for both steady-state and unsteady-state conditions. The key feature is how the mode of operation controls the magnitude of deposit resistance, Rd- One other point of interest from Eqs. (10.1) and (10.2) is the role of permeate (filtrate) viscosity, nri, which can have a strong influence on production. For example, the effect of temperature on water viscosity would mean at 10°C the flux would only be about 60% of that at 30°C for the same TMP. It is important to note that ti refers to permeate and not feed viscosity, which can be much higher than water, as found in a typical membrane bioreactor. 

Efficient stem cell expansion is a key bottleneck for clinical application and commercialization of stem cell therapy. Membrane bioreactors may make a significant contribution due to its important features such as possibility for uniform chemical and biochemical conditions within the bioreactor, low or even zero hydrodynamic shears, large surface-to-volume ratios, and physical separation between two cell types but allowing biochemical signaling between them. For example, it may be possible to culture the feeder cells on one side of the membrane, while culturing human embryonic stem cells on the other. In this way human embryonic stem cells are not mixed with the feeder cells, which eliminates the need for later difficult separation, but get the biochemical signals from the feeder cells that are necessary to proliferate embryonic stem cells (e.g., Choo et al., 2006 Klimanskaya et al., 2005). 

The rising need for new separation processes for the biotechnology industry and the increasing attention towards development of new industrial eruyme processes demonstrate a potential for the use of liquid membranes (LMs). This technique is particularly appropriate for multiple enzyme / cofactor systems since any number of enzymes as well as other molecules can be coencapsulated. This paper focuses on the application of LMs for enzyme encapsulation. The formulation and properties of LMs are first introduced for those unfamiliar with the technique. Special attention is paid to carrier-facilitated transport of amino acids in LMs, since this is a central feature involved in the operation of many LM encapsulated enzyme bioreactor systems. Current work in this laboratory with a tyrosinase/ ascorbate system for isolation of reactive intermediate oxidation products related to L-DOPA is discussed. A brief review of previous LM enzyme systems and reactor configurations is included for reference. 

There is no commonly accepted definition of a membrane reactor but the term is applied to membrane (including liquid membrane) processes and devices whose function is to perform chemical conversion, coupling and combining chemical and transport processes, using the unique contacting features of membranes. As a rule, functional definition of this term includes fermentation, catalysis, separation of the products and their enrichment. A few published reviews at this time are available [98-104]. In most of pubhcations the bioreactors, based on enzymes or whole cells, impregnated into the membrane pores (immobihzed or supported hquid membranes) or deposited on the membrane surfaces are discussed. 

A membrane (bio)reactor is a piece of chemical equipment in which a chemical or biochemical reaction, coupled with the separation features of a membrane system, allows the addition of a reactant or the removal of products from the reaction environment. Membrane reactors and bioreactors are, therefore, an example of the combination of two operations in a single... 

Work with these types of electrodes enables to achieve steady-state current conditions within a short time-period. Primarily proposed for monitoring and control of blood and tissue oxygen tension [10], the electrode systems with selective membranes were manufactured and used in continuous oxygen measurement in a wide variety of aqueous solutions [11]. The sensors of this type, called Clark electrodes, are described in chapter 6 of this volume. Improvements designed for continuous monitoring in industrial bioreactors may be found in section 6 of chapter 3. The most important feature of the membranes used in these sensors is their selectivity which prevents poisoning the electrode system and deteriorating the adherent electrolyte solution. 

Bioreactors. Bioreactors that utilize hving cells are typically called fermenters. There are several different types of bioreactors mechanically stirred or agitated tanks bubble columns (cylindrical tanks that are not stirred but through which gas is bubbled) loop reactors, which have forced circulation packed-bed reactors membrane reactors microreactors and a variety of different types of reactors that are not easily classified (such as gas-Uquid reactors and rotating-disk reactors). Biochemical engineers must choose the best bioreactor type for the desired purpose and outfit it with the right instrumentation and other features. 

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