Protein soil release using protease as monitored with a quartz crystal microbalance

Detergency is a complex procedure comprising both chemical and mechanical processes. In order to fully understand the chemical process, it is necessary to uncover its basic steps by setting up a simplified modeling system. In this study, we attempt to find the key to the detergency mechanism by revealing the adsorption of enzymes and surfactants onto proteins and the degradation and subsequent release of the proteins using a quartz crystal microbalance (QCM) measurement that can quantify minute weight changes in water over time. We first examine three different proteins-gelatin, ovalbumin (OvA), and keratin. The frequency change of a QCM is traced for the release of solid protein by Nagarse(R) from the surface of a gold electrode. As observed in former studies of dissolved protein, the synergistic effects are confirmed for release by protease/nonionic surfactants, i.e., C-12(EO)(7) and C-16(EO)(7). Adding anionic surfactants-sodium dodecylbenzene-sulfonate (DBS) or sodium dodecylsulfonate (SDS)-enhances the release rate at near the critical micelle concentrations. The amount of adsorption of the enzyme to gelatin increases in the presence of anionic or nonionic surfactants.