A Comparison of the Activity Reduction Occurring in Two Detergent‐Assisted Protein (Cellulase and Lysozyme) Foam Fractionation Processes

Abstract

Foam fractionation has the potential to be an inexpensive alternative to current protein drug concentration or separation methods; however, it has a few drawbacks. One is the fact that not all proteins form a foam layer when aerated at low concentrations. The other is the possible protein denaturation caused during the foaming process. Adding a detergent to the nonfoaming protein solution causes it to foam when aerated. Here, cellulase and lysozyme are studied as model proteins in this process. By themselves, both cellulase and lysozyme solutions hardly form a foam layer when aerated at concentrations below 1000 mg/L (1000 ppm). The addition of 100 mg/L of cetyltrimethylammonium bromide (CTAB) to a 200 mg/L cellulase solution increases the foam volume and makes it possible to almost quadruple (relative to the initial bulk concentration) the concentration of the resulting cellulase foam solution. The foaming, however, reduces the cellulase activity. Diluting the foam with β‐cyclodextrin regains some of the lost activity because β‐cyclodextrin strips CTAB away from the cellulase, which allows the cellulase to refold to its native state. CTAB detergent does not work well with lysozyme, but the addition of SDS detergent leads to a tripling of the concentration of lysozyme solution without any reduction in enzymatic activity.