Direct relationship between the growth of suspension cells and pH changes in medium was also discovered: When culture medium pH decreased from 5.80 to 4.10 within the
first 9 days culture, DWincreased slowly. When pH went up to 5.19 between 9 and 13 days following subculture, exponential increase in DW occurred. After 15 days, pH and
DW changed little (Fig. 5).