Expanded liquid antisolvent (ELAS) precipitation is a modification of the well-known supercritical antisolvent (SAS) process. Different from SAS, ELAS allows the micronization of water-soluble compounds using an antisolvent formed by supercritical carbon dioxide (scCO(2)) and an organic solvent, used to improve water solubility in carbon dioxide. In this work, ELAS was proposed for the micronization of lysozyme, an enzyme characterized by an intense antibacterial activity, using as antisolvents mixtures formed by scCO(2) + acetone and scCO(2) + isopropyl alcohol. Microparticles of lysozyme, with a mean diameter ranging between 2.8 and 13.8 mu m, varying the kind of co-antisolvent, the concentration of the enzyme in the liquid solution and the position of the operating point in the ternary diagram formed by water, carbon dioxide and the process co-antisolvent were obtained. The obtained powders were characterized using XRD and FT-IR. These analyses showed that ELAS process did not influence solute integrity. UV-vis analysis revealed that lysozyme enzymatic activity was not significantly altered. The best results were obtained using acetone, measuring a biological activity of 95% with respect to the native protein. (C) 2015 Elsevier B.V. All rights reserved.