Release of miniantibodies from E. coli cells into the supernatant at low and high cell densities

By chemical permeabilization of E. coli cells with detergents and membrane active peptides considerable amounts of the periplasmic anti-PC-miniantibodies can be released. Releases of active miniantibodies of 31%, respectively of 38%, were obtained by exposing low cell density suspensions to nonionic detergents like Triton X-100 and tetraethyleneglycolmonodecylether. At high cell densities releasing levels of 40% and 56% were observed for these detergents. The addition of cationic, membrane active peptides (PMBN, polylysine 115, magainin II and melittin) led to release of up to 20% of active miniantibodies at low cell densities. The excretion of miniantibodies at low cell densities was increased up to 35% by phospholipase A2. Interestingly, the membrane associating properties of the anti-PC-miniantibodies influenced the permeability of the outer membrane and the excretion of beta-lactamase.