Fermentation course of recombinant E. coli cells expressing totally 2.1 g L−1 of single‐cell antibody fragment scFv‐phOx (P) by using the XylS/Pm expression system. Lines: 1, growth curve; 2, soluble P in periplasm; 3, soluble P in growth medium; 4, insoluble P in cytoplasm; 5, total soluble + insoluble P (data imported from Sletta et al., 2004; 2007).