The comparison of the commonly used pulse feeding of methanol to P. pastoris cultures in shake flasks with the quasi continuous feeding clearly showed clearly that the commonly applied standard protocol is not favorable to optimize recombinant processes, mainly due to the longterm starvation phases. Commonly such optimization is performed in bioreactors, which however are not available for many of the molecular biology laboratories. We show here a simple solution by applying a quasi-continuous feed profile, which is a method commonly used in bioreactors. However, the developed feeding device is not limited to such simple applications, but pre-determined feed functions and even feed-back control of the feed rate on the basis of measured parameters can be easily programmed and principally turn the shake flask into a bioreactor.