Optimization of antibody fragment production in Bacillus megaterium: the role of metal ions on protein secretion

Abstract

The effect of the concentration of metal ions in minimal media has been shown to be very important for the production and secretion of the antibody fragment D1.3 scFv in Bacillus megaterium YYBm1. The best media compositions for biomass and antibody fragment formation were evaluated using a genetic algorithm. The screening was carried out in 96 microtiter deep well plates with 900 μL cultivation volume. In 7 generations, 240 different kinds of media were tested, key elements for production and secretion were detected and a 117% increase in production of antibody fragment compared to the previously used medium could be achieved. In addition, media with a higher biomass formation (+84%) or with both more biomass and a higher production of antibody fragment (Pareto-front members) were found. Interestingly the best media for protein production and secretion were different in their composition, with regards to the metal ion concentration levels. From data derived experimentally and from the genome, magnesium was shown to be one of the key components of the metal ions tested for biomass formation and especially for production and secretion of the antibody fragment D1.3 scFv.