Growth curves were determined by inoculating approximately1 g fresh weight of suspension cells filtered using sterile GFC fil-ters in 250-ml Erlenmeyer flasks containing 50 ml of medium. Cells were harvested every 3 days to determine the pH and optical density. The absorbance of the suspension culture was recorded using a UV–spectrophotometer (UV-2450, Shimadzu) to determine abso-lute cell growth.