In this research, the biosorption of lead by Lactobacillius bulgaricus
was investigated. The mechanism for the biosorption was similar to ionic exchanger. The media pH, weight of dried biomass and initial lead concentration were investigated at ambient temperature. At high acidic solution (pH<1.5) and also in alkaline condition, there was no significant absorption. In these experiments the highest biosorption of lead occurred at pH value of 6 and the biomass concentration of 4.5 g/l. The removal efficiency of 88.8 percent was obtained with initial lead concentration of 50 mg/l. It was found that Lactobacillus bulgaricus
was highly efficient in low ion concentration (less than 100ppm), however for the lead concentration higher than 100ppm the percent of removal was low (less than 50 percent).