The optimization of long-term storage method for the probiotic cyanobacterium Arthrospira sp. as part of the MELiSSA (Micro-Ecological Life Support System Alternative) project

The filamentous cyanobacterium Arthrospira sp known also as spirulina shows the ability to produce oxygen and remove CO2 via photosynthesis,. It can also be used as a food supply since it produces edible biomass because of its high amount with protein. For these reasons it was chosen for the Micro-Ecological Life Support System (MELiSSA) project of the European Space Agency for space applications. The problem is that the only way to preserve Arthrospira sp is sub-culturing which is a problem for its conservation due to the high contamination risks and possible genetic modification. We still need to optimize a method for long term preservation without any changes. For that purpose different preservation methods were tested, it includes the preservation at -80�C using cryoprotectants like DMSO and trehalose; preservation following metabolic conditioning such as trehalose accumulation after salt stress. After cell resuscitation, cell physiological state was be assessed. The latter includes cell viability evaluation through culturing, microscopy and flow cytometry techniques. The cryopreservation at -80�C using cryoprotectants shows the best results ; cells were able to regrow after one week preservation with 10% DMSO + 10% trehalose and 15% trehalose + 5% DMSO. Fluorescence microscopy observation shows that the cells were s still healthy. For the following metabolic conditioning (trehalose accumulation after salt stress) before freezing, we measured successfully the amount of the cellular trehalose produced after a salt chock. The highest trehalose concentration was observed with 0.750M and 1M NaCl after 30 minutes of incubation. However the physiological state of the cells could not be assessed after the crypreservation with and without 10% DMSO.