Fig 2.

Comparison of process data from the feed phase of cultivations performed with the plasmid-based [BL21(DE3)(pET30aSOD), open circles] system and the plasmid-free [BL21(DE3)::TN7<T7-SOD>, filled circles] system. Determination of the induction of recombinant gene expression was conducted at feed hour 7. (A) Plasmid copy number. (B) Levels of the stress marker guanosin-3′,5′-tetraphosphat (ppGpp). The dashed line indicates the time point of induction. Data shown are derived from three independent replicate experiments (n = 3).