Figure 2. Statistical effects of yeast extract (YE), milk whey retentate (MWR) and fetal bovine serum (FBS) at a confidence level of 90% obtained for the 2³ star expanded full factorial design on viable cell concentration in midexponential phase (X_me), viable cell concentration in stationary phase (X_s), viability in midexponential phase (V_me) and cell growth rate (µ). Cells were inoculated in different media at a final concentration of 2.5 x 10⁵ cells.ml^-1 and cultivated at 28ºC. *Significant effects at 90% confidence level. (L) refers to linear terms in the mathematical model. (Q) refers to quadratic terms.