Dephosphorylation of casein with "antartic" alkaline phosphatase and effect of the dephosphorylated casein on chymosin secretion. A. SDS-PAGE (12%) of casein and dephosphorylated casein after alkaline phosphatase treatment. Four subunits of casein were detected after blue-silver Colloidal Coomassie staining (left). ProQ Diamond Staining (rigth) showed a significant decrease in the signal intensity of the bands corresponding to the dephosphorylated subunits of casein (subunits β and κ) after treatment with "antartic" alkaline phosphatase (lane +AP). Tandem mass spectrometry was used to identify the casein subunits. B. Production of chymosin at 24 and 48 h in cultures without any addition, supplemented with 10 g/L or 5 g/L casein (C+) or with 5 g/L partially dephosphorylated casein (C+P-). C. Production of chymosin at 24 and 48 h using MDFA3 medium without supplement, supplemented with 3 g/L casein, or with 3 g/L commercially dephosphorylated casein (Sigma).