Fig. 2

Evaluation of bacterial growth and recombinant protein accumulation. Growth curves of E. coli (A) and A. tumefaciens (B) carrying pTRAc vectors (Additional file 1: Table S3) for the expression of DsRed or IgG1 under control of different promoters. DsRed and IgG1 concentrations in E. coli (C) and A. tumefaciens (D) per cell dry mass were determined by ELISA. Cell-mass specific recombinant protein concentrations were calculated using a dry mass to OD_600nm conversion factor of 0.396 g⁻¹ (E. coli) and 0.409 g.⁻¹ (A. tumefaciens) [55, 56] and a wet mass to dry mass conversion factor of 0.2. DsRed and IgG1 concentration in E. coli (E) and A. tumefaciens (F) fermentation broth were quantified by ELISA. The sampling time points were shifted by ± 1.5 h to display significant differences between samples. IgG1 and DsRed accumulation levels in PCPs (G) using different promoters. Western blot of triplicate PCP extracts (H) using plasmids with different promoters for the expression of DsRed (top row) and IgG1 (bottom row). DsRed was detected using a rabbit anti-His₆ primary antibody and an alkaline phosphatase (AP)-labeled goat anti-rabbit secondary antibody, whereas IgG1 was detected using an AP-labeled goat anti-human antibody. Full-size blots can be found as Additional file 2: Fig. S2 “Risk_and_bioburden_knödler_et_al_full-size_blots_v2”. CaMV35S—double-enhanced cauliflower mosaic virus 35S promoter with strong activity in plants; bla—β-lactamase promoter with activity in bacteria; T7—bacteriophage T7 promoter with minimal activity in bacteria unless the corresponding polymerase is expressed. Data are means ± SD (n = 3 biological replicates, two-way ANOVA with Bonferroni correction and a significance threshold of α = 0.05; *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001)