RI amounts and activities normalized per cell amount from samples of batch and fed-batch bioreactor cultivations without and with addition of DTT that was either added once (open circles) or repeatedly (one pulse per hour, filled circles). The first addition of DTT was performed always two hour after induction of RI synthesis. A: Total (white bars) and soluble (black bars) RI amount as mg per g cell dry weight [mg (g CDW)-1]. B: RI activities in normalised crude extracts, in kilo units per gram of wet cell weight [kU (g CWW)-1]. The data are from 3 independent assays.