A 1-mL sample of bacterial stock suspension was transferred into nutrient broth (Okon et al., 1977) in 500mL Erlenmeyer flasks containing 100 or 300mLnutrient media, respectively,
which were agitated on a rotary shaker at 125 rpm, 30±2 ◦C for 48 h. The optical density (OD600) was taken using a spectrophotometer (Ultrascope III).