Phytases (myo-inositol hexakisphosphatephos phohydrolase, EC 3.1.3.8) catalyze the release of phosphate from phytates. Many of the cereal grains, legumes and oilseeds store phosphorus in phytate form. Phytases are used in many areas such as in food industry, in preparation of myo-inositol phosphates, in the paper industry and in soil improvement. In this study, isolation and characterization of phytase enzyme from Lactobacillus spp. (ATCC) strain was studied. Phytase production from bacterial strains was determined by zone production formed around colonies after 48 hours of incubation at 30 °C in MRS medium. The phytase enzyme that was partially purified by precipitation of ammonium sulphate from Lactobacillus acidophilus bacteria extracellularly was put into liquid culture medium, and its optimum pH and optimum temperature values were measured. Optimum activity of the enzyme derived from Lactobacillus acidophilus bacterium was at 30 °C and pH 5.0. It was observed that Lactobacillus acidophilus’s extracellular enzyme maintains its 90% of activity at 10-100 °C for 120 minutes. Effects of certain metal ions on activity of phytase enzyme derived from Lactobacillus acidophilus were also investigated. Of these, CuCl₂, MnCl₂ and CoCl₂ inhibited enzyme activity significantly. And, FeCl₂ has increased enzyme activity by 164%. Based on these results, the phytase enzyme of Lactobacillus acidophilus is considered suitable for use in many industrial areas, in fertilizer and food industries in particular, due to its thermal stability and resistance against metal ions.