The Bioreactor Express service has its first experiment: the BioAsteroid experiment from the University of Edinburgh will investigate how gravity affects the interaction between microbes and rock in reduced gravity. The experiment uses the KEU-RK Experiment Units, each featuring two bio-mining reactors (BMR) capable of culturing microbial biofilms on the surface of a flat rock slide. The two BMRs are totally independent and are equipped with reservoirs for chemicals and a culture chamber. The culture chamber allows gas exchange during the experiment. Moreover, the transparency of the culture chamber allows the visual observation of the microbial film without disassembling the unit. The scientific protocol is driven by the embedded electronics following a programmed timeline. After re-entry on Earth both the culture slide and the process fluids will be retrieved for analysis. The experiment is scheduled to fly in October next year.