Optimising IPTG and Lactose Induction of Recombinant Expression with Flow-based Online Analysis

Sammanfattning: The induction of recombinant expression in bioprocesses is associated with high costs, but still suffers from unoptimised standard procedures with high use of IPTG. A flow-based online method for enzymatic analysis of recombinant expression in E. coli could greatly help in mapping induction behaviour, and assembly and programming of a FlowSystem for automatic sampling was done. The process was never able to handle cell samples as they caused counter pressure in the system, and the program and the hardware would have to be further optimised to control dispersion and mixing, but if done properly, this method could be an important tool for deeper induction studies. The enzymatic assay was also used offline and showed that concentrations of IPTG lower than 1 mM could be feasible, at least in some situations, but concentrations as low as 0.1 mM would be too low. Lactose as an inducer was only tested in a smaller study and no clear evidence of whether it could work – either on its own, or in concert with IPTG – was found. In conclusion the study indicates that lower IPTG concentrations could be viable for bioprocesses, but further research is needed to accurately optimise the concentration.