RESUMEN
Lead enters the human body through water, food, air and accumulates in bones instead of calcium. It can damage nervous system, kidneys and genital system especially in children and also affects hemoglobin synthesis. To optimize the environment conditions to increase the biosorption with Saccharomyces cerevisiae as well as cell immobilization and determination of its efficiency associated with degree of biosorption. This was a cross-sectional study carried out at the Laboratory Center, Islamic Azad University, Sciences and Researches Division, Tehran [Iran] during 2009-2010. The strain of Saccharomyces cerevisiae used in this study was obtained from Lorestan yeast manufacturer, Lorestan, Iran. All factors affecting biosorption including the initial lead concentration, contact time, and pH were investigated. Entrapment method was used to immobilize cells. The maximum biosorption capacity of 80 mg g[-1] dw was observed at the following conditions: contact time 2 h, initial lead concentration 500 ppm, and pH 4.5. The metal biosorption capacity of pretreated yeast strain by autoclave was 35.3 mg g[-1] dw. Also, the biosorption capacity of immobilized cells was almost doubled compared to that of free cells. Regarding the data found in our study, non-pretreated and stabilized Saccharomyces cerevisiae is a suitable biosorbent for removal of lead ions from environment