Figure 3

Tyrosinase production of freshly transformed E. coli JM109 (pMFvpt) during the fed-batch cultivation. Cells were grown at 32°C and induced with 1.25 mM IPTG at an OD₆₀₀ value of 34. (A) Example of the fed-batch process applied in this study. The time course of the dissolved oxygen (pO₂) (blue color), pure oxygen input (red color) and the OD₆₀₀ values (green color) is shown. The dashed arrow indicates the time when feeding started; the solid arrow indicates the onset of induction. (B) Time-profiles of cell density (OD₆₀₀) and volumetric activity (U mL^-1) of tyrosinase during the fed-batch cultivation. The dashed arrow indicates the time when feeding started, the solid arrow indicates the onset of induction. (C) SDS-PAGE of proteins prepared from extracts of E. coli JM109 (pMFvpt). Samples were taken after 22 h just before induction (lanes 1, 4 and 7), after 28 h (6 h induction, lanes 2, 5 and 8), and after 40 h (18 h induction, lanes 3, 6 and 9). Lanes 1–3, insoluble proteins; Lanes 4–6, soluble proteins; lanes 7–9, total proteins. The arrow indicates the position of tyrosinase in the gel. Molecular weight standards are shown on the left.