Packed reactors immobilized enzyme

Shiraishi, F., T. Hasegawa, S. Kasai, N. Makishita, and H. Miyakawa. 1996. Characteristics of Apparent Kinetic Parameters in a Packed-Bed Immobilized Enzyme Reactor. Chemical Engineering Science 51 (ll) 2847-2852. 

FIGURE 121 Flow injection manifolds for accommodation of minicolumns packed with immobilized enzyme, (a) ER before sample injection (b) ER in the analytical path and (c) ER inside the detection system. ER = enzyme reactor (solid support with immobilized enzyme), S = sample, R = reagent, C = carrier stream, IV = injection valve (or a similar injection device) RC = reaction coil, D = detector, and W = waste. 

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. 

A commercial pectinase, immobilised on appropriately functionalised y-alumina spheres, was loaded in a packed bed reactor and employed to depolymerise the pectin contained in a model solution and in the apple juice. The activity of the immobilized enzyme was tested in several batch reactions and compared with the one of the free enzyme. A successful apple juice depectinisation was obtained using the pectinase immobilised system. In addition, an endopolygalacturonase from Kluyveromyces marxianus, previously purified in a single-step process with coreshell microspheres specifically prepared, was immobilised on the same active support and the efficiency of the resulting catalyst was tested. 

The packed bed reactor is particularly lu ul for reactions involving solid-phase reagents such as cati Psts, immobilized enzymes,and metallic reducing agents [641,642,646,647,658]. Since solutions are added in this isase, there are no... 

When comparing experimental and theoretical results it should be mentioned that in addition to processes that are related to the reaction mechanisms but not considered in the model (see Section 4.3.6), several assumptions related to the operational mode are also made. For example, in the analytical model developed for the packed bed reactor it was assumed that no diffusion limitations are operative and that the immobilized enzymes are distributed in... 

Another type of mass transfer equipment, shown in Figure 6.2d, is normally referred to as the packed- (fixed-) bed. Unlike the packed column for gas-liquid mass transfer, the packed-bed column is used for mass transfer between the surface of packed solid particles (e.g., catalyst particles or immobilized enzyme particles) and a single-phase liquid or gas. This type of equipment, which is widely used as reactors, adsorption columns, chromatography columns, and so on, is discussed in greater detail in Chapters 7 and 11. 

The immobilization of lipase on CoFoam was considered effective and simple. The low resistance to fluid flow made CoFoam a viable support to be used in large reactors. The enzyme can easily and quickly be loaded in any packed bed reactor. 

The packed-bed reactor configuration commonly employed with immobilized enzymes yields a higher degree of conversion or higher space-time yield than a CSTR, the typical configuration for soluble enzymes. Examples are the nitrile hydratase-catalyzed process to 5-cyanovaleramide (5-CVAM) (Chapter 7, Section 7.1.1.3) or the decarboxylation of D,L-aspartate to D-aspartate, L-alanine, and C02 (Section 7.2.2.5). 

Right Profiles of decrease in F(t)/F(0) for intraparticle diffusion-influenced zero-order reaction with spherical immobilized enzyme particles packed in the reactor operated under a constant conversion policy (x = 0.99). Enzyme activity decays as E(t)/E(0) = exp ( kd t). 

A great savings in enzyme consumption can be achieved by immobilizing the enzyme in the reactor. In addition to the smaller amount of enzyme required, immobilization often increases the stability of the enzyme. Several designs of immobilized-enzyme reactors (lERs) have been reported, with open tubular and packed bed being the most popular. Open-tubular reactors offer low dispersion, but have a relatively small surface area for enzyme attachment. Packed-bed reactors provide extremely high surface areas and improved mass transport at the cost of more dispersion. 

The immobilized enzyme was removed from the tube and rinsed with D.I. water, followed sequentially by 2N urea solution, 2N NaCl solution and tris buffer, pH 7.5, containing 0.2% sodium azide and 20 mM CaClg, then stored at 4 C. About 0.18-0.2 g of immobilized enzyme beads were used to slurry pack stainless steel 10 cm x 2.1 mm column reactors. Complete details of enzyme preparation and assay for activity are described elsewhere [12],... 

An equation equivalent to the Michaelis-Menten equation has been derived for immobilized enzymes in packed-bed reactor systems, and is given in Eq. 4.24 ... 

As noted earlier in this chapter, the apparent Km values of immobilized enzymes vary with the thickness of the diffusion layer surrounding the particles. In packed-bed enzyme reactors, the thickness of this layer varies with the mobile phase flow rate. Faster flow rates produce smaller diffusion layers and therefore K m values that more closely approximate the true Km of the enzyme. This effect has also been observed with the ficin-CM-cellulose reactor, and plots of K m against flow rate Q obtained at different mobile phase flow rates are shown in Figure 4.14. 

The value of a thermometric signal is calculated by means of a mathematical formulation of the heat and material balance in the reaction system, represented by the microcalorimetric column packed with an immobilized enzyme. The microcalorimetric column with an IMB can be defined as the continuous packed bed reactor depicted in Fig. 3. The balance equations were derived according to the following simplifying assumptions, which had been previously verified [27] ... 

Immobilization, dehned as the physical confinement or localization of an enzyme into a specihc micro-environment, has been a very common approach to prepare enzymes for aqueous as well as nonaqueous applications. For nonaqueous enzymol-ogy, immobilization improves storage and thermal stability, facilitates enzyme recovery, and enhances enzyme dispersion. In addition, immobilized enzymes are readily incorporated in packed bed bioreactors, allowing for continuous operation of reactions. Moreover, lyophilized enzyme powders often aggregate and attach to reactor walls, particularly when the water activity is moderately high. The major disadvantage of immobilization is low activity, induced by pore diffusion mass transfer limitations and by alteration of protein stmcture. For enzymes in nonaqueous media, the following broad categories of immobilization exist ... 

In packed bed reactors the enzyme-catalyzed reaction is carried out in a column of 100 pl-10 ml volume. The column is filled with tiny particles bearing the immobilized enzyme. The continuously formed reaction product is indicated colorimetrically or electrochemically. Enzyme carrier materials with advantageous flow behavior are porous glass with pores of a defined size, organic polymers, like nylon powder, and inorganic polymers. 

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