Effects of freeze-drying and microwave vacuum freeze-drying on the activity of IgY: From the perspective of protein structure

Freeze-drying (FD) is often used for therapeutic proteins and other biological drugs to extend their shelf life, but it usually reduces the activity and stability of the protein and has a longer drying cycle. A microwave-assisted freeze-drying (MFD) was proposed to produce immunoglobulin of yolk (IgY) preparations. The effects of FD and MFD on the immunological activity and structure of IgY with different amounts of trehalose were investigated. Results showed that lyophilization led to a partial loss of secondary structure in IgY, which resulted in the activity loss. As the trehalose content increased from 0% to 5%, the activity retention of MFD samples increased from 20.31% to 75.57%, which was comparable to FD samples (from 23.57% to 67.78%). However, MFD had a shorter drying cycle when compared with FD. MFD can be a potential alternative to FD as a common therapeutic protein drying method.