DEVELOPMENT OF A MINIATURE BIOREACTOR FOR CONTINUOUS-CULTURE IN A SPACE LABORATORY

A new type of miniature bioreactor for continuous culture of yeast cel ls in space laboratories has been developed. Silicon microtechnology h as permitted the integration of numerous functions and systems in a vo lume of 87 x 63 x 63 mm(3) and a weight of 610 g. The 100 ml of fresh medium can be delivered at variable flow rates to the cultivation cham ber (volume 3 ml) by means of a micropump. The culture is agitated by a magnetic stirrer. Microsensors monitor pH, temperature and redox pot ential. The decrease of pH occurring during the cultivation of Sacchar omyces cerevisiae is compensated electrochemically. A window allows th e inspection of the culture status. Samples of up to 1 ml can be drawn through a silicone rubber septum. The data measured by the sensors ar e transmitted on-line to the ground station during operations in space . The bioreactor had to fulfil several requirements related to the saf ety regulation of the space agencies. In particular, new materials had to be selected and tested for their biocompatibility. The instrument has now passed all space and biological qualification tests and will b e used in an experiment selected by ESA for the International Microgra vity Laboratory-2 Mission in Spacelab in July 1994. This paper gives t he results of the functional and biological tests and a detailed descr iption of the instrument.