Mass transfer studies on immobilized α-chymotrypsin biocatalysts prepared by deposition for use in organic medium

Abstract

Mass transfer limitations were studied in enzyme preparations of α‐chymotrypsin made by deposition on different porous support materials such as controlled pore glasses, Celite, and polyamides of different particle sizes. It is the onset of mass transfer limitations that determines the position of the activity optimum with respect to enzyme loading on each support. The evidence of various experiments indicates that internal diffusional limitations are the important mechanism for the observed mass transfer limitations. External diffusion was not found to play an important role under the conditions used, and it was also found that when immobilizing multilayers of enzyme the buried enzyme molecules are active to a large extent. An extreme situation is observed on Celite at very high loadings. Under these conditions, this support is expected to have its pores completely filled with packed enzyme molecules, and then it is the diffusion within the enzyme layer that determines the observed rate. As the enzyme loading increases, the area of contact between the deposited enzyme layers and the liquid solution inside the pores diminishes, causing a decrease on the observed rate of an intrinsically fast reaction which apparently is incongruous with the presence of more enzyme in the system. This work shows that mass transfer limitations can be an important factor when working with immobilized enzymes in organic media, and its study should be carried out in order to avoid undesired reduced enzyme activities and specificities. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:364–373, 1998.

Factors Governing the Activity of Lyophilised and Immobilised Lipase Preparations in Organic Solvents

“…[20,28,29] At low loadings, low specific activity has been described as being due to partial enzyme inactivation, whilst at high loadings, mass transfer limitations can decrease the specific activity. In the current study, the specific activity at a loading of 55 mg g À1 was considerably higher than that at 6.6 mg g À1 (Table 1).…”

Development of glucose oxidase-based bioanodes for enzyme fuel cell applications

“…Moreover, it is generally accepted that immobilized enzyme systems experience a loss of activity due to mass transport problems through the matrix [16], leading to the decrease of power output of the corresponding EFC device.…”

Optimization of Chlorophyllase-catalyzed Hydrolysis of Chlorophyll in Monophasic Organic Solvent Media

“…In a heterogeneous system, the enzyme catalysis may be affected by the diffusion rate of substrate through the boundary layer at the surface of the enzyme particles, external diffusion, as well as in their inside, internal diffusion [25]. It is therefore important to ensure that the diffusional limitations do not affect the kinetics of chlorophyllase-catalyzed hydrolysis of chlorophyll in the neat organic solvent mixture.…”

“…2) show that an increase in the agitation speed from 0 to 200 rpm resulted in a 75% increase in the specific activity of chlorophyllase. This increase may be attributed to a decrease in the size of enzyme particles and/or in the thickness of the boundary layer surrounding the solid enzyme, which could have led to an increase in the rate of the external substrate diffusion [25]. The overall results reveal that the external diffusional limitations occurred within the agitation speed range of 0 to 200 rpm.…”