A new biosorbent, methylated yeast (MeYE), was prepared for the adsorptive separation of proteins from aqueous solutions. Yeast was methylated in a 0.1 M HCl methyl alcohol solution at room temperature. About 80% of the carboxylic groups of yeast could be methylated within 9 It. The adsorption of egg albumin onto MeYE was studied to evaluate the protein adsorption ability of MeYE. At near neutral pH, egg albumin was scarcely adsorbed onto unmethylated yeast and the adsorbed amount of egg albumin increased with increasing methylation degree. The amount of egg albumin adsorbed onto MeYE increased with increasing pH from 4 to 7 and steeply decreased above pH 7. The Langmuir isotherm was applied to determine the apparent adsorption constant and the saturated adsorbed amount of egg albumin on MeYE. Both the apparent adsorption constant and the saturated adsorbed amount increased with the degree of methylation. The saturated adsorbed amount of egg albumin onto MeYE having methylation degree 77% was 8.41 x 10(-6) mol g(-1) or 0.378 g g(-1) at near neutral pH. (C) 2003 Elsevier Inc. All rights reserved.