Fed Batch Production of Bacterial Ghosts Using Dielectric Spectroscopy for Dynamic Process Control
The Bacterial Ghost (BG) platform technology evolved from a microbiological expression system incorporating the phX174 lysis gene E. E lysis generates empty but structurally intact cell envelopes (BGs) from Gram negative bacteria which have been suggested as candidate vaccines, immunotherapeutic agents or drug delivery vehicles. E lysis is a highly dynamic and complex biological process that puts exceptional demands towards process understanding and control. The development of a both economic and robust fed batch production process for BGs required a toolset capable of dealing with rapidly changing concentrations of viable biomass during the E lysis phase. This challenge was addressed using a transfer function combining dielectric spectroscopy and soft sensor based biomass estimation for monitoring the rapid decline of viable biomass during the E lysis phase. The transfer function was implemented to a feed controller, which followed the permittivity signal closely and was capable of maintaining a constant specific substrate uptake rate during lysis phase. With the described toolset, we were able to increase the yield of BG production processes by a factor of 8 10 when compared to currently used batch procedures reaching lysis efficiencies >98% This provides elevated potentials for commercial application of the Bacterial Ghost platform technology.
Microorganisms