Enhancement of Continuous Crystallization of Lysozyme through Ultrasound

Protein drugs have attracted extensive attention from the academic community. However, crystallization of proteins is difficult and the yield of current main technologies is too low, which limits their large-scale industrial production. In this work, enhancement of continuous crystallization of lysozyme under an ultrasonic field was explored. A plug-flow tubular crystallizer, which was separated into a nucleation zone and a growth zone, was applied. The effect of ultrasound on steady-state time, crystal habit, particle size, particle size distribution, and the process yield was evaluated based on univariate analysis experiments. It was found that ultrasound can shorten the time for continuous crystallization to reach a steady state, reduce the degree of aggregation, and promote nucleation. Furthermore, the separation of the growth zone from the nucleation zone in the ultrasonic-assisted continuous crystallization can further increase the size of the lysozyme crystals, which would help in increasing the yield.