Adaptastat--a new method for optimising of bacterial growth conditions in continuous culture: Interactive substrate limitation based on dissolved oxygen measurement.

A new method for continuous cultivation of microbes, called adaptastat, is described. It involves automatic adaptation of microbial cultures to their maximum feeding rates and avoids substrate accumulation. The state of the culture is estimated at intervals by briefly (and markedly) decreasing the substrate feeding rate and measuring, via the dissolved oxygen response, the time taken to exhaust the residual substrate. The method has been exemplified by cultivating Escherichia coli on single carbon sources (glucose, acetate, succinate, and fully deuteriated medium based on deuteriated succinate) and also by simultaneous limitation of two feeding channels (succinate/acetate and glucose/ammonium chloride). Several possible applications of the adaptastat technology are presented. The method provides an efficient means of labelling microbial components and products with stable isotopes. In particular, adaptastat technology can be used to adapt disabled bacterial strains to the use of simple, inexpensive substrates. It can also be used more generally in the study of microbial cell cultures, for example for the determination of maximum specific growth rates and the stoichiometric ratio of utilisation of two nutrients in conditions of simultaneous limitation.