We need to deal with the degradation according to the time when it occurs. If the degradation occurs during the culture process, we need to optimize the culture conditions, which may be due to over-abundance of nutrients, etc., and can be improved by optimizing the medium and temperature of culture; if we exclude the degradation occurs during the cultivation process, it may be the degradation occurs during the purification process, and the solution is to add protease inhibitors, treat the environment at a low temperature to reduce the physical shear force.