A designed biosurfactant protein for switchable foam control

Abstract

Making and breaking foams: A facile method for foam control is reported using a designed biosurfactant. The new biosurfactant is based on a four‐helix bundle design which is interfacially active across a broad pH range. At pH 8.5 stable foam forms, yet decreasing the pH to 7.5 causes rapid foam dissipation. This unique behaviour can be linked to subtle molecular and specific‐ion effects which lead to switchable changes in the state of the foam thin film (see picture).