Integration of Nitrifying, Photosynthetic and Animal Compartments at the MELiSSA Pilot Plant

Abstract

MELiSSA (Micro Ecological Life Support System Alternative) is developing bioregenerative Life Support technologies for long-term Space missions. The MELiSSA concept is conceived as a loop with several compartments, each one performing a specific function, providing all together edible material production, atmosphere regeneration and water recovery with a concomitant use of wastes, i.e., CO2 and organic wastes. Each one of the compartments is colonized with specific bacteria or higher plants depending on its specific function. The MELiSSA Pilot Plant is a facility designed for the terrestrial demonstration of this concept, hosting laboratory rats as a crew mock-up mimicking the respiration of humans. Currently, the MELiSSA Pilot Plant focus on the integration of three compartments: Compartment 3 (nitrifying packed-bed bioreactor based on the co-culture of immobilized Nitrosomonas europaea and Nitrobacter winogradsky), compartment 4a (an air-lift photobioreactor for the culture of the edible cyanobacteria Limnospira indica with concomitant oxygen production) and Compartment 5 (an animal isolator with rats as mock-up crew). The output from these tests shows a high robustness and reliability and the performance of oxygen producing and oxygen consuming compartments is successfully demonstrated under transitory and steady-state conditions. This contribution reports on the current state of development of the MELiSSA Pilot Plant Facility and the most recent results of the integration work.

Space bioprocess engineering as a potential catalyst for sustainability

“…Although primarily designed for air revitalization and waste management 85 , the MELiSSA was inspired by sustainable environmental models on Earth. Although elements of the MELiSSA have been tested in flight 86 , they were limited to experiments using rodents 87 . Another BLSS project, EDEN ISS, has been proved more extensively on a larger scale, although only on the ground 88,89 .…”

Stoichiometric model of a fully closed bioregenerative life support system for autonomous long-duration space missions

“…The nitrifying bioreactor as defined in the MELiSSA project is a cylindrical packed-bed bioreactor with polystyrene beads that are colonized by a biofilm of Nitrosomonas europaea and Nitrobacter winogradsky (Cruvellier et al, 2016;Garcia-Gragera et al, 2021). The nitrification of ammonia happens in two steps, each step carried out by one of the bacterial species (Cruvellier et al, 2016):…”

“…4.1.4 Compartment 4: food production 4.1.4.1 Compartment 4a: photoautotrophic cyanobacteria growth The edible microalgae Limnospira platensis and indica (previously Arthrospira platensis and indica) are cyanobacteria that consume nitrate and CO 2 that are produced in other compartments of the loop, and generate oxygen and food for the crew (Clauwaert et al, 2017;Alemany et al, 2019;Sachdeva et al, 2021). Limnospira is grown inside a gas lift photobioreactor with illumination and a gas injection system (Garcia-Gragera et al, 2021;Poughon et al, 2021). Since a custom biomass composition is used in our model, a new stoichiometric balance had to be calculated (generated biomass is dry mass): (Pannico et al, 2022).…”

“…This results in nutrients and CO 2 for microalgae and plants (C4a and C4b) that, in turn, provide food, oxygen, and fresh water for the crew (C5), thus closing the loop (Hendrickx and Mergeay, 2007;Clauwaert et al, 2017;Vermeulen et al, 2020a). The operational pilot plant at Universitat Autònoma de Barcelona consists of a number of connected MELiSSA compartments and demonstrates a part of the system's entire metabolic loop (Gòdia et al, 2004;Garcia-Gragera et al, 2021). Mathematical models of the MELiSSA loop have been developed and improved since the beginning of the MELiSSA project in 1989 (MELiSSA, 1989;Dussap and Gros, 1991).…”

Perspectives for plant biology in space and analogue environments

“…An example of BLSS is the MELiSSA (Micro-Ecological Life Support System Alternative) loop by the European Space Agency (ESA) that aims to sustain astronaut life in space missions to reduce the initial payload and dependency from Earth 8 . The MELiSSA loop is made of interconnected compartments among which the requirements of the higher plant compartment need to be fulfilled at least in part by the outputs of other compartments 9 . As well, the species/cultivar choice and environmental control are dictated by the need to meet the requirements of the other compartments (e.g., oxygen requirements of the animal crew) in addition to the generally accepted requirements including short cultivation cycles, reduced plant size, high harvest index, and resistance to diseases.…”