Detection and Identification of New Growth Phases on the S-shaped Growth Curve of Suspension Culture Cells Number
It has been shown that in the exponential (logarithmic) growth phase (EGPh), the condition of constancy and maximum specific growth rate of the number of cells in a batch suspension culture is only acceptable for one case out of actually unlimited number of options of cell population age distribution. The condition for constancy and minimum time for cells generation in EGPh is only realized for a definite time interval rather than for the whole EGPh period. In EGPh, the following new growth phases were revealed and identified: the first transition growth phase (1-TGPh), stable growth phase (SGPh) and the second transition growth phase (2-TGPh). Formulae for the determination and prediction of the dynamics of number and age composition of suspension culture cells in EGPh are given. This permits to determine the time of the appearance of the cells age composition at which the concentration of a product of interest is maximum in the suspension culture. Thus, the optimal time of discharge-filling for obtaining the maximum amount of the product can be precisely determined. The detection of EGPh and SGPh is also of practical importance when the optimal synchronization time of the suspension culture should be determined because SGPh is the only stage when the suspension culture cells have the highest homogeneity by cell cycles duration. Various cytophotometric studies should also be performed in SGPh as this period is a time when morphometric parameters of cells can be most probably correlated with their age.