Production of vtPA in a high-cell-density fermentation. (A) The cell density, expressed in grams (wet weight) of cells, is shown for four fermentations: FÅ113/pTrcvtPA-h6, induced (•); FÅ113/pTrcStIIvtPA-h6, induced (○); FÅ113/pTrcTorAvtPA-h6, induced (▪); and FÅ113/pTrcTorAvtPA-h6, uninduced (□). The arrow indicates the time of induction with 1 mM IPTG. (B) Relative plasminogen activation for cytoplasmic (c) (open bars) and periplasmic (p) (gray bars) fractions. All data were normalized to the activity measured for the cytoplasmic or periplasmic fraction of FÅ113 expressing Δss-vtPA. (C) Quantitative periplasmic vtPA yield assessed by ELISA as described in Materials and Methods. The ELISA data are the averages of two replicate experiments. The asterisk indicates that the yield was measured for the cytoplasmic fraction since no Δss-vtPA was localized in the periplasm. Only data from fractionation experiments in which ≥95% of the β-galactosidase activity was in the cytoplasmic fraction are shown.