Role of a Tween 20-containing antifoaming agent in renaturation of foam-denatured pepsin during defoaming

The foam-induced enzyme denaturation, which often results in a large activity loss, is a common phenomenon in foam fractionation of enzymes. To reduce it effectively, we used a Tween 20-containing antifoaming agent to assist the renaturation of the enzyme molecules adsorbed at the gas-liquid interface during defoaming with pepsin as a model enzyme. We studied the roles of the antifoaming agent and its ingredients in renaturation of the adsorbed pepsin molecules. The results show that during defoaming, Tween 20 in the antifoaming agent was able to assist the adsorbed pepsin molecules to restore their native structures as soon as they were desorbed from the gas-liquid interface. The other ingredients, including polydimethylsiloxane, polyether L61 and aluminum silicate, did not affect the pepsin structure during defoaming. However, they enhanced the Tween 20-assisted renaturation of the adsorbed pepsin molecules by increasing the defoaming efficiency. Furthermore, the separation of the antifoaming agent from pepsin in the foamate had no significant effect on its specific activity. When the addition amount of the antifoaming agent in the foamate was 15.0‰ (v/v), almost all the adsorbed pepsin molecules were reactivated. Therefore, the foam-induced pepsin denaturation was reduced effectively without any changes of the foam fractionation process itself. The results are important to improve the performances of foam fractionation of enzymes.