Effects of detergent on enzyme adsorption onto solid surfaces

Enzyme adsorption on charged solid surfaces can be enhanced or inhibited by switching the solution pH above or below the enzyme isoelectric point. Such mechanism was achieved through another approach in this study using detergent formulations. Two detergent formulations showed opposite effects on subtilisin A (SA) and lysozyme (used as a control) adsorption, in which one enhanced the adsorption of SA but not lysozyme, while the other gave the opposite trend. The film thickness of the adsorbed SA from the first detergent formulation (i.e., Tide) reached 2.34 nm while its film thickness when adsorbed from the second detergent formulation (i.e., Gel) was undetectable. Contrarily, the thickness of the adsorbed lysozyme films from these two detergent formulations was similar to 0 and 3.95 nm, respectively. Such observations might be explained in terms of enzyme-detergent interactions, which might lead to the formation of complexes having different affinities for a given surface. It could also be due to the coating of the original surface with a thin film of the detergent, with a thickness higher than the Debye length, and hence preventing the electrostatic interactions between the underlying surface and the adsorbed enzyme. The outer layer of the coating film would have different chemistries for those two formulations. It was found that the enhancement of enzyme adsorption by the detergent solution is switchable based on the detergent solution pH. Understanding the effects of detergent formulations on enzyme adsorption is of significant importance since detergent formulations-containing enzymes are widely used in several applications (e.g., detergency). Such understanding might assist in optimizing the enzyme-detergent interactions, leading to a better cleaning performance.