Enzyme reactor design

Up to now general reaction engineering principles have been discussed. Now we turn to enzyme reactor design. 

Besides the classical engineering question of reactor choice, the most important point in enzyme reactor design is the aspect of enzyme reuse, either by immobilization or by separation from the product stream. Batch processes without enzyme reuse are only possible if the costs of the biocatalyst are negligible. Different reactor techniques addressing the aspect of enzyme reuse are discussed in the following sections. 

Fig. 3.1 Scheme for the construction of a model for enzyme reactor design and performance evaluation... 

The analysis will be done in three steps. In the fist step, differential equations will be developed by combining enzyme kinetics and mass transfer to obtain the substrate (and product) profile within the biocatalyst particle in the second step, local effectiveness factor profiles will be obtained from the previous step in the third step a global effectiveness factor will be obtained by adequately averaging that distribution. This global effectiveness factor describes the behavior of the biocatalyst particle as a whole and will be obtained in terms of measured and calculated parameters, being a useful way of incorporating IDR into enzyme reactor design and performance evaluation, as considered in section 5.3. 

Effect of Diffusional Restrictions on Enzyme Reactor Design and Performance in Heterogeneous Systems. Determination of Effectiveness Factors. Batch Reactor Continuous Stirred Tank Reactor Under Complete Mixing Continuous Packed-Bed Reactor Under Plug Flow Regime... 

Effect of Thermal Inactivation on Enzyme Reactor Design and Performance... 

Enzyme Reactor Design and Performance Under Non-Modulated and Modulated Enzyme Thermal Inactivation... 

Behavior of enzyme reactors under no inactivation was presented in section 5.2. Now, the effect of enzyme inactivation will be incorporated. Conventional design of enzyme reactors considering one-stage first-order inactivation without modulation will be firstly presented in this section. In the next section, enzyme reactor design will be developed for more complex inactivation mechanisms considering modulation. 

CPBR with chitin-immobilized (3-galactosidase (Illanes et al. 1998a) is presented to illustrate enzyme reactor design under modulated thermal inactivation. Diffusional restrictions are in this case negligible, the enzyme is inhibited by the product galactose competitively and neither glucose nor lactose at high concentrations are inhibitors (Illanes et al. 1990), so that Fig. 5.14 simplifies to the scheme in Fig. 5.18. 

Illanes A, Fajardo A (2001) KineticaUy controlled synthesis of ampiciUin with immobihzed penicillin acylase in the presence of organic cosolvents. J Mol Catal B Enzym 11(4-6) 587-595 Illanes A, Wilson L (2003) Enzyme reactor design under thermal inactivation. Crit Rev Biotechnol 23(l) 61-93... 

Immobilized enzyme reactors are increasingly popular due to their advantages over conventional catalysts. For efficient reactor design and performance prediction, quantitative knowledge of reaction kinetics and the factors affecting them is required. In this chapter, enzyme catalytic mechanisms are described and the kinetic models developed from these mechanisms are discussed. The chapter also discusses the kinetics of immobilized enzymes and their related mass transfer effects. Diffusion restrictions are described with a particular focus on packed bed reactors. The chapter concludes with a brief discussion of immobilized enzyme reactor design and scale-up. 

Fig. 27. Activity loss a/a of Acylase enzym resign with the reaction time t of the enzymatic deaccylation of Penicillin G to 6-Aminopenicillanic acid (reactor design see Fig. 28)...

The simplest design for an enzyme reactor is to merely have the substrate and enzyme in two merging buffer streams followed by a reaction delay coil (Fig. 12). The delay... 

Fig. 12. On-line enzyme reactor system designs, merging stream system (Top) and immobilized-enzyme reactor system (Bottom). A = mobile phase, B = enzyme solution...

A great savings in enzyme consumption can be achieved by immobilizing the enzyme in the reactor (Fig. 12). In addition to the smaller amount of enzyme required, immobilization often increases the stability of the enzyme. Several designs of immobiliz-ed-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. 

In addition, Chapters 6 and 7 could be reserved for the enrichment of the treatment of kinetics, and Chapter 10 can be used for an introduction to enzyme kinetics dealing with some of the problems in the reactor design chapters. 

This chapter describes the different types of batch and continuous bioreactors. The basic reactor concepts are described as well as the respective basic bioreactors design equations. The comparison of enzyme reactors is performed taking into account the enzyme kinetics. The modelhng and design of real reactors is discussed based on the several factors which influence their performance the immobilized biocatalyst kinetics, the external and internal mass transfer effects, the axial dispersion effects, and the operational stabihty of the immobilized biocatalyst. 

W. II. Pitcher Design and Operation of Immobilized Enzyme Reactors. - S. A Barker Biotechnology of Immobilized Multienzyme Systems. - R. A Messing Carriers for Immobilized Biologically Active Systems. -P. Brodelius Industrial Applications of Immobilized Biocatalysts. - B. Solomon Starch Hydrolysis by Immobilized Enzymers. 

If a certain process can produce a product, it is important to know how fast the process can take place. Kinetics deals with rate of a reaction and how it is affected by various chemical and physical conditions. This is where the expertise of chemical engineers familiar with chemical kinetics and reactor design plays a major role. Similar techniques can be employed to deal with enzyme or cell kinetics. To design an effective bioreactor... 

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