Single colony of each bacterial strains was cultured in 25 ml Plate Count Broth (PCB) at 37oC, shaking for 18 h. After that, cell density was adjusted to the range of 0.1-0.5 OD at 600 nm using a spectrophotometer (Thermo Spectronic model 4001/4, USA) and spread on Plate Counting Agar (PCA).