Effect of shear on the inactivation kinetics of the enzyme dextransucrase

Abstract

An inactivation model previously developed to characterize the rate of enzyme activity loss in unstirred solutions was extended to take into account orthokinetic interactions resulting from convective mixing. A synergistic relationship between shear rate and temperature was observed; the rate of inactivation of the enzyme dextransucrase was unaffected by the action of shear below 25 degrees C, but was increased by the shear rate at 30 degrees C. Shear rate does not appear to influence the equilibrium between native and denatured dextransucrase either directly in solution or indirectly by augmenting the turnover of the gas-liquid interface. However, a second-order plot of the inverse of relative activity (A(O)/A) versus Gt (shear rate x time) of dextransucrase at a constant temperature was linear because of the influence of shear on the coagulation of the denatured enzyme. The addition of 0.01 g L(-1) of polyethylene glycol (MW 20,000) blocked this coagulation reaction, thereby completely inhibiting the shear-induced inactivation of dextransucrase at 30 degrees C.

Utilization of cross‐linked laccase aggregates in a perfusion basket reactor for the continuous elimination of endocrine‐disrupting chemicals

“…Furthermore, in unstirred reactors, the air-liquid interface is typically saturated with denatured enzymes, thus limiting the inactivation of more protein. Agitation of the reaction medium causes the movement of the enzyme molecules present at the interface and is apparently responsible for the renewal of the species at this boundary causing the denaturation of more enzyme (Lencki et al, 1993).…”

Effects of shear on proteins in solution

“…Proteins might be denatured at the interface and then mixed back into the solution as the interface is continually renewed. Lencki et al(1993) showed that shear might enhance chemical or thermal enzyme inactivation, possibly by promoting coagulation of denatured protein, reducing renaturation. There may also be other effects attributed to "shear"; for long exposure times, one might worry about heavy metal, plasticizer, lubricant or sealant contamination, or local hot spots near an impeller bearing, and it has been known for a long time that proteins can also be denatured at solid-liquid interfaces (Sandwick and Schray 1987).…”

Deactivation of isoamylase and β-amylase in the agitated reactor under supercritical carbon dioxide

“…In order to better understand the mechanism by which agitation speed alters enzymatic deactivation under high pressure, the reaction mechanism proposed by Lencki et al for shear-induced dextransucrase inactivation was adopted to analyze our experimental data on the deactivation kinetics of isoamylase and b-amylase [30][31][32]. The reasons why the aforesaid model was adopted to analyze the deactivation behaviors of isoamylase and b-amylase under SC-CO 2 environment in this study were as follows: (1) Aside from dextransucrase, the proposed inactivation model or its modified version has been successfully applied to a variety of enzymes such as urease, carboxypeptidase A, chymosin, and catalase [30][31][32].…”

“…The reasons why the aforesaid model was adopted to analyze the deactivation behaviors of isoamylase and b-amylase under SC-CO 2 environment in this study were as follows: (1) Aside from dextransucrase, the proposed inactivation model or its modified version has been successfully applied to a variety of enzymes such as urease, carboxypeptidase A, chymosin, and catalase [30][31][32]. (2) The influence of agitation, which is frequently encountered in the cases of industrial-scale stirred tank reactors with sheared environment, is taken into account in the proposed inactivation model.…”