The Modification of Dissolution Kinetics and Solubility of Lysozyme Crystals by Ionic Liquids

Knowing about the dissolution kinetics and solubility is necessary for controlling crystallization separation process of lysozyme. In this study, the impact of four ionic liquids (ILs), namely, 1-butyl-3-methylimidazolium tetrafluoroborate [C₄mim]BF₄, 1-butyl-3-methylimidazole chloride [C₄mim]Cl, 1-butyl-3-methylimidazole bromide [C₄mim]Br, and 1,3-dimethylimidazolium iodide [dmim]I, on the dissolution rate of lysozyme was determined in an aqueous solution at 20 ℃, pH 5.01, under 101.3 kPa. The results revealed that the dissolution rate of lysozyme increased with increasing concentrations of [C₄mim]BF₄ and [C₄mim]Cl, while it remained stable with increasing concentrations of [C₄mim]Br. In contrast, the dissolution rate gradually decreased with increasing concentrations of [dmim]I. This suggests that the interaction between lysozyme molecules is influenced by the ILs, leading to variations in the dissolution rates. Additionally, the effect of anions and cations on the equilibrium solubility was analyzed. The results indicated that the order of anionic and cationic effects on equilibrium solubility is as follows: BF⁴⁻ < Cl⁻ < Br⁻ = [C₄mim]⁺ < [dmim]⁺ < I⁻. Furthermore, dissolution kinetic models were established, which could be used to predict the dissolution behavior of large molecules like lysozyme in ILs aqueous solution. These findings have significant implications for the design of crystallization process and optimization of parameters during lysozyme recovery.