Denaturation of Proteins upon Adsorption to Bubble Surfaces

Foam fractionation is a process that has potential for application in the separation of proteins from aqueous solution because the molecules adsorb to the foam bubbles. However, some proteins are known to denature by unfolding upon adsorption to a gasliquid interface and, since the utility of unfolded proteins in pharmaceutical applications is low, it is possible that the use of foam fractionation for the enrichment of proteins is compromised through denaturation. In this work, the dynamic surface tensions of samples of aqueous solutions of Bovine Serum Albumin have been measured. One sample was repeatedly foamed by shaking whence the foam was collapsed, causing many cycles of adsorption and desorption in order to give the proteins opportunity to unfold, and the results were compared to a control sample that was spared the pre-foaming treatment. Results showed that the dynamic surface tension of the pre-foamed sample was lower than the control, and therefore demonstrated in a relatively simple experiment that protein denaturation occurred during the foaming process. In addition, the dynamic surface tensions of samples of bovine milk, both controlled and pre-bubbled, have been measured that show a denaturation effect caused by proteins adsorbed to bubbles.