Enzyme kinetics and engineering

Abstract

. Particular attention is given to methods of attaching enzymes to solid supports, and to factors, such as pH and temperature, which affect the reaction rate. Recent theories accounting for the high selectivity and high rate of enzyme reactions, calculations taking into consideration the effects of diffusion, methods for analyzing kinetic data, and proposals for enzyme reactors are evaluated. Also reviewed are recent methods for extraction of enzymes from cells, procedures for synthesizing enzymes artificially, and techniques for isolating and purifying enzymes. Enzymes are of great interest to scientists and engineers not only because of their essential role in the metabolic pathways of biological systems, but also because of the vast opportunities they open up for innovations in chemical technology. Their ability to enhance the rate of chemical reactions by many orders of magnitude at room temperature and their amazing specificity towards substrates make them ideal industrial catalysts. Enzymes provide a way of eliminating many of the operational difficulties of high pressures and temperatures often encountered in chemical catalytic processes while at the same time avoiding costly and time consuming product purifications.One of the major obstacles to the industrial use of enzymes is the lack of fast, efficient methods of extracting enzymes from the cells of biological organisms. The enzyme purification methods currently available are suitable for the production of enzymes on a small scale for research applications. However, the isolation of large quantities of enzymes from microorganisms has not reached its full potential. Procedures for synthesizing enzymes artificially are being investigated, but these are still in a preliminary research stage.Enzyme reactions usually follow the well-known Michaelis-Menten kinetics under steady state conditions. The constants in the rate equation are very dependent on the physical conditions of the media in which conversion is taking place. Most enzymes exhibit an optimum pH and temperature for reaction to occur and are very sensitive to small deviations from these optimum values. The ionic strength and the presence of metal ions and inhibitors in solution can affect the rate of reaction significantly. Unusual conditions of temperature, pressure, and the presence of some organic compounds can denature the protein and completely inactivate it. The enzyme environment must therefore be carefully controlled in order to obtain the largest possible rate of conversion.In the few cases where enzymes are used industrially, the reaction is usually carried out in a homogeneous liquid phase. To isolate the products, the enzyme must be denatured by heating or by hydrolysis. It is very important to develop ways of insolubilizing enzymes to allow complete recovery of the catalyst. This would also facilitate the development of continuous heterogeneous enzymatic reaction processes. Many insolubilization procedures are being investigated, ranging from the covalent attachment of the protein to ...

Effects of pH and Trace Minerals on Long-Term Starvation ofLeuconostoc mesenteroides

“…8, the model equation is consistent with the cell decay data for different pH values. It is interesting that the effect of pH on cell decay kinetics produces a curve shape similar to that for enzyme deactivation kinetics as a function of pH (10,18). From the analogy between the effects of pH on cell decay kinetics and enzyme deactivation, a mechanism of cell decay at high and low pHs can be explained based on enzyme deactivation at different pH values (15,29) and the Michaelis pH function theory (23,31).…”

Glucose Isomerase: A Case Study of Enzyme-Catalyzed Process Technology

“…• • Mosbach and Larsson (1970) amino acids Smolarsky, et al (1973) antibiotics • • Marshall, et al (1972); Berman and Murashige-C1973); Hamilton, et al (1974 a) recently been given by Faith,et al (1971), Carbonell and Kostin (1972), Wingard (1972a, 1972b~ Zaborsky (1973, and also by papers in this volume.…”

Measurement of Radial Transport in Slug Flow Using Enzyme Tubes

“…The recent introduction of open tubular heterogeneous enzyme reactors provides, however, a simple tool for such measurements. Enzymes possess high catalytic activity in aqueous media at room temperature and they can be immobilized by covalent bonding to a suitable carrier without loss of activity (Carbonell and Kostin, 1972).…”