The aim of this research study is to obtain highly efficient Saccharomyces boulardii biotherapeutic strains through protoplast fusion techniques.Methods:the selected fusants F1 (S.b.M1 X S.b.M2) (ad X lys) and F2 (S.b.M2 X S.b.M3) (lys ~arg) and their parents; S.b.Ml(ad),S.b.M2 (lys) and S.b.M3 (arg) as well as the wild type strain (S.boulardii) were examined by Electron microscope and tested for their anti-microbial activities,tolerance to low pH and 3% bile salt.Results:the number of intact cells were about 3000,4500 and 5500 cells / ml in the protoplast suspensions of S.b.M1,S.b.M2 and S.b.M3,respectively.