Lipase from Nigella sativa seeds was immobilized by adsorption on Celite 535 from phosphate buffer solutions varying pH values of 5.0-8.0 at 25 degrees C. Langmuir isotherms described the adsorption equilibria well for lipase adsorption at all pH range. The saturation capacity for adsorption of lipase increased from 14.5 to 24.3 mg g(-1) Celite as the adsorption pH was reduced from 8 to 5, but the adsorption equilibrium constant remained constant and was determined to be 1.92 x 10(5) M-1. The adsorbed enzymes showed different activity values depending on the pH of the adsorption medium. The immobilized enzymes prepared at pH 6 displayed the highest activity values.