25 Nov Spirulina in space
To organize long-term manned space missions, the MELISSA (Micro Ecological Life Support System Alternative) project, fostered and coordinated by the European Space Agency (ESA), studies and develops a bioregenerative life support system, based on the use of micro organisms and higher plants which would recycle CO2 and organic wastes into O2, water and food in an integrated system (**70).
It consists in an interconnected group of several compartments.
Two of these compartments (photosynthetic compartments) are responsible of the energy collection in the system allowing them to fulfil the roles of food and oxygen generators. Spirulina (Arthrospira) platensis, is the blue-green alga which has been chosen as the O2 producer due to its good photosynthetic capabilities, its high protein content and its health benefits, which render the microalga a high value food complement, while in a neighbour compartment a selection of higher plants are cultivated; the inclusion of both higher plants and microalgae allows for a healthy diet for the crew as well as for an efficient recycling.
Other compartments perform: (a) the decomposition of most of the waste compounds by anaerobic thermophilic bacteria to volatile fatty acids and CO2 and (b) the further decomposition of hardly metabolizable higher plant compounds, such as fibres and lignin, by aerobic fungi.
In between the previously described compartments, two other compartments undertake the biotransformation steps of volatile fatty acids, hydrogen and some sulphur containing compounds by photoauto/heterotrophic bacteria and the conversion of the ammonia generated by the thermophilic bacteria into nitrate by nitrifying bacteria.
Nitrate and CO2 produced by bacterial fermentations are further used by the Spirulina microalga (http://www.esa.int/Enabling_Support/Space_Engineering_Technology/Melissa).
Similar experiments were performed by NASA and other National Space Agencies for the design of a Controlled Ecological Life Support System-CELSS (**71) (https://space.nss.org/settlement/nasa/).
(**) Literature on the subject