wPin , biomass specific intracellular product concentration [mg/g]; wPex , biomass specific extracellular product concentration [mg/g].
Results and Discussion
The process parameters temperature and ยต are important factors in bioprocess development and are known to have an impact on leakiness of different E. coli strains (Table 1). Although conclusive, mechanistic understanding is still missing. In this study, we performed characterization of the novel E. coli X-press strain in fed batch cultivations by investigating the influence of temperature andqS,0 (qS at the beginning of induction) on growth, productivity, lysis and leakiness, with the aim of understanding the behavior of the strain and finding a cultivation strategy that allows the successful control of product location. For comparison of the X-press strain to a benchmark strain, we choseE. coli BL21(DE3), since it is the most widely used E. coli strain for recombinant protein production (Jia & Jeon, 2016; Rosano, Morales, & Ceccarelli, 2019). Three combinations of cultivation temperature and qS,0 (30/0.25, 25/0.13, 35/0.13) were first applied using the model protein SpA. The most favorable production conditions were then tested again with the second model protein VHH.