The bioreactors are essential components for the sustainability of spatial explorations. They allow recycling waste and make useful products like food or oxygen. Nowadays several technologies of bioreactors make use of cyanobacteria which are large microorganisms (100 µm) performing photosynthesis. However despite the great realization made in the field few limitations still remain. For instance, the need for filtering the reactor stream is prone to clogging; the high turbidity of the concentrated microorganism prevents the optimal light exposition of the culture bulk and limit the photosynthesis. Here we aim to develop a novel generation of bioreactors that make use of the acoustic levitation to circumvent these problems. In acoustic resonators, objects in suspension (particles, cells or micro-organisms) can be moved by Acoustic Radiation Forces (ARF) generated by ultrasounds. Once ARF are generated in the liquid, objects can be gathered in acoustic traps and maintained in acoustic levitation. Previous work of our team demonstrated that ARF are well suited to manipulate a large number of any microscopic objects (1 to hundreds of microns) with a 1 to 4 MHz ultrasonic source. This approach is very promising. It shows that one can carry out cell cultures in aggregates sheets trapped within the liquid bulk. Moreover a simple, relatively low-cost, compact and low-energy device is enough to achieve acoustic trapping. ALISS project consists in designing a new experimental bioreactor adapted to the zero-G flights where levitating cyanobacteria will be cultured and monitored during its operation. In a large extent, we would like to contribute with new insights and methods to the ESTEC laboratory that develop the European project of circular life support systems.
