Dynamic Experiments for Bioprocess Parameter Optimization with Extreme Halophilic Archaea

The to-date studies on extreme halophiles were focused on shake flask cultivations. Bioreactor technology with quantitative approaches can offer a wide variety of biotechnological applications to exploit the special biochemical features of halophiles. Enabling industrial use of Haloferax mediterranei, finding the optima of cultivation parameters is of high interest. In general, process parameter optimizations were mainly carried out with laborious and time-consuming chemostat cultures. This work offers a faster alternative for process parameter optimization by applying temperature ramps and pH shifts on a halophilic continuous bioreactor culture. Although the hydraulic equilibrium in continuous culture is not reached along the ramps, the main effects on the activity from the dynamic studies can still be concluded. The results revealed that the optimal temperature range may be limited at the lower end by the activity of the primary metabolism pathways. At the higher end, the mass transfer of oxygen between the gaseous and the liquid phase can be limiting for microbial growth. pH was also shown to be a key parameter for avoiding overflow metabolism. The obtained experimental data were evaluated by clustering with multivariate data analyses. Showing the feasibility on a halophilic example, the presented dynamic methodology offers a tool for accelerating bioprocess development.