Reactors immobilizing

Flame reactor immobilizes metals into a nonhazardous, vitrified slag even at low metal... 

Enzymatic bioreactor Immobilized enzyme biosensor Immobilized enzyme reactor Immobilized microfluidic enzyme reactor (IMER) Membrane reactor... 

In a continuous stirred tank reactor, a cmstant flow of reacliai substrates is fed to the reactor, where the immobilized lipase is suspoided in an agitated vessel. The main character of this type of reactitm is that Ihae is no tanperature or concentration gradients due to efficient mixing that promotes intimate contact of the reaction mixture with the immobilized lipase. Like batchwise reactors, immobilized lipase can be retained within the bioreactor by filtration. This is known to have lower construction cost. However, it requires larger volumes than a PER to achieve the same reaction. Commonly, a microfilter is provided at the bioreactor outlet to prevent immobilized lipase from leaving the reactor. 

Another important factor that causes a decrease in the lipase activity is the depressurization rate, which is a step commonly used to separate the products. It has been reported that lipase activity decreases with an increase in the number of depressurizations (GieBauf et al., 1999). A rapid release of dissolved CO2 in the water bound to the enzyme may cause structural change to the enzyme (Lin et al., 2006). This irreversible change with depressurization was studied by Randolph et al. (1991). However, this problem is only encountered in the batch system and results in enzyme inactivation. In continuous flow systems, however, the depressurization step takes place after the product leaves the reactor. Immobilized lipases are retained inside the reactor and not exposed to depressurization. 

I Gil Torro, JV Garcia Mate, J Martinez Calatayud. Spectrofluorimetric determination of vitamin K3 by a solid phase zinc reactor immobilized in a flow injection assembly. Analyst 122 139-142, 1997. 

Tubular reactor Immobilized Low-pressure mercury lamp Pollutant degradation [170]... 

Can the contaminant be brought to a reactor or constmcted wetland where biological systems, microbial or plant, can extract and immobilize the contaminant ... 

In most cases, hoUow fibers are used as cylindrical membranes that permit selective exchange of materials across their waUs. However, they can also be used as containers to effect the controUed release of a specific material (2), or as reactors to chemically modify a permeate as it diffuses through a chemically activated hoUow-fiber waU, eg, loaded with immobilized enzyme (see Enzyme applications). 

In open fibers the fiber wall may be a permselective membrane, and uses include dialysis, ultrafiltration, reverse osmosis, Dorman exchange (dialysis), osmotic pumping, pervaporation, gaseous separation, and stream filtration. Alternatively, the fiber wall may act as a catalytic reactor and immobilization of catalyst and enzyme in the wall entity may occur. Loaded fibers are used as sorbents, and in ion exchange and controlled release. Special uses of hoUow fibers include tissue-culture growth, heat exchangers, and others. 

Another version of a fluidized-bed reactor has been introduced by Vogelbusch (Austria). This reactor has an internal recirculation loop set up by means of a high flow impeller. The system utilises porous glass beads for immobilizing the cells. However, glass beads may not work with all types of cells. 

A significant advantage of immobilized enzymes is the total absence of catalytic activity in the product. Moreover, the degree of substrate-to-product conversion can be controlled during processing, eg, by adjusting the flow rate through a packed-bed column reactor of immobilized enzyme. 

Membrane reactors, where the enzyme is adsorbed or kept in solution on one side of an ultrafHtration membrane, provides a form of immobilized enzyme and the possibiHty of product separation. 

During operation, the immobilized enzyme loses activity. Most commercial enzymes show decay as a function of time (Eig. 12). The glucose isomerase ia a reactor is usually replaced after three half-Hves, ie, when the activity has dropped to around 12.5% of the initial value. The most stable commercial glucose isomerases have half-Hves of around 200 days ia practical use. To maintain the same fmctose content ia the finished symp, the feed-flow rate is adjusted according to the actual activity of the enzyme. With only one isomerization reactor ia operation, the result would be excessive variations ia the rate of symp production. To avoid this, several reactors at different stages ia the cycle of enzyme decay are operated ia combiaation. 

Enzymatic Reactors Adding free enzyme to a batch reactor is practical only when the value of the enzyme is relatively low. With expensive enzymes, reuse by retaining the enzyme with some type of support makes great economic sense. As some activity is usually lost in tethering the enzyme and the additional operations cost money, stabihty is very important. However, many enzymes are stabilized by immobilization thus, many reuses may be possible. 

Methods of immobilization have already been discussed, and various reactor configurations are possible. An enzyme immobilized on... 

Press, 1973. Lee, Y. Y. and G. T. Tsao, Engineering Problems of Immobilized Enzymes, ]. Food Technol, 39, 667 (1974). Messing, R. A., Immobilized Enzymes for Industrial Reactors, Academic Press, 1975. Torry, S., Enzyme Technology, Noyes DataCorp., Park Ridge, New Jersey, 1983. 

The nonphosphorylated compounds may be readily obtained by chemical or, preferentially, by mild phosphatase hydrolysis of the 1-phosphates. Reactor design17 and enzyme immobilization techniques18 have been evaluated for efficient practical syntheses. Owing to the narrow specificity... 

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. 

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