For long term space missions, higher plants are necessary to be included in life support systems. The Micro Ecological Life Support System Alternative (MELiSSA) project of European Space Agency (ESA) is based on a closed life support system where microbial and higher plant compartments support the consumer’s compartment. Plants consume the possible recycling wastes (waste water and CO2) and provide fresh food, potable water and oxygen to the crew. One of the key points for this kind of study is to maintain a system which recycles all the elements C, H, O, N, S, P, etc. That is why, the study is based on the modelling of conversion stoichiometries ; they are the results of the control parameters of the system (physical limitations of mass and energy exchanges). As a preliminary step, we have established leaf metabolic model (a sub model of the plant biochemical model) involving central carbon metabolism using metabolic techniques, elementary flux mode analysis (EFMA) and metabolic flux analysis (MFA). It is associated to an integrated approach of energetics and central metabolism. Due to data limitations, the leaf metabolic model was constructed taking the biomass composition of lettuce (Lactuca sativa) from United States Department of Agriculture (USDA) and validated with the experimental data where lettuce grown in controlled Environment Systems Research Facility (CESRF) of University of Guelph (Canada). For the first approach, the model is satisfying and promising ; it can predict the biomass production connecting the physical plant growth factors (light, CO2 and water availability, etc.) along with time course growth and biomass composition. However, our results show the lack of sufficient data ; hence, various kinds of measurements required for more accurate model predictions are proposed. The future model must be able to control and manage the plant growth for human survival knowing the fluxes from other compartments of MELiSSA loop. Further, the approach described here can be used more generically in all kinds of metabolic studies and modeling, especially for studying simultaneous and/or consecutive photosynthetic and respiratory metabolisms.
