(269e) Enzymatic Hydrolysis of Proteins in Bulk Solutions and at Liquid/Air, Liquid/Solid Interfaces: Effect of Surfactants | AIChE

(269e) Enzymatic Hydrolysis of Proteins in Bulk Solutions and at Liquid/Air, Liquid/Solid Interfaces: Effect of Surfactants

Authors 

Svitova, T. F. - Presenter, University of California at Berkeley
Radke, C. - Presenter, University of California-Berkeley


Proteases are common components of automatic dishwashing and laundry formulations assisting in the removal of proteinaceous stains. Mechanistic understanding is lacking of adsorption and kinetic behavior of protease/surfactant mixtures in the cleavage of surface-immoblized proteins. We study the kinetics of protein hydrolysis by the serine protease Subtilisin Carlsberg employing fluorescent assay for the bulk aqueous solution, optical waveguide lightmode spectroscopy (OWLS) for protein-stain removal from a solid surface, and flow tensiometry for protein removal from the liquid/air interface. We find that all surfactants studied reduce bulk proteolysis rates due to substrate-screening. However, these same surfactants enhance protein removal from both the solid/water and air/water interfaces. Moreover, the mixed enzyme/surfactant solutions perform better than their single-component counterparts at both the solid/water and air/water interfaces. A simple Langmuir-Michaelis-Menton (LMM) kinetic model is proposed to describe the kinetics of the simultaneous enzyme adsorption and substrate cleavage of the surface-immobilized protein layers. This model well describes the enzymatic-cleavage dynamics of different solid-surface-immobilized protein substrates removal. The LMM model is extended to describe the dynamics of protein-stain removal by protease-surfactant mixtures. We find that surfactant and enzyme compete for the surface-immobilized protein active sites when applied together.