Why is it necessary to add carrier protein to some recombinant protein solutions?

The protein solution is usually not very stable when it is frozen at low concentration. During the freeze-thaw process, some proteins in the solution will adhere to the container wall. If the initial concentration of protein is low, the above reasons may lead to a further significant decrease in protein concentration. Therefore, the carrier protein is used to reduce such losses. The most commonly used carrier proteins include bovine serum albumin (BSA), human serum albumin (HSA) or fetal bovine serum (FBS). The usual concentration of these carrier proteins is 0.1%. According to empirical data, if the concentration of recombinant protein is lower than 0.5 mg/mL, it is recommended to add some carrier protein.