The future human exploration of space depends on the ability to provide for the metabolic needs of a crew, reducing the amount of re-supply required from Earth. One of the key-challenge is to recreate conditions suitable for human survival and well-being, providing water, food, air and shelter. This issue has been addressed by developing several types of Life Support System (LSS) over the years, studying the possibility to introduce biological entities in the loop. Among all the different aspects involving the human survival far from Earth, one of the most important is the quality and nutritional value of the food consumed by astronauts. In extreme environments, such as Moon, Mars or deep space, the consumption of high-quality, nutrient-rich and nutrient-bioavailable food becomes fundamental to the survival and well-being of the crew. To address this issue a prototype for the autonomous cultivation of microgreens, the Microgreens Production Unit (MPU) has been designed, assembled and ground-tested. Microgreens can be used as a fresh, ready-to-eat and healthy dietary supplement, thanks to their high nutritional quality and beneficial effects on human body, such as reducing risk of cancer and space-related effects. The system was designed to be compliant with International Space Station (ISS) standard payload rack, based on the Mid-Deck Locker Equivalent (MLE) drawer of the EXpedite the PRocessing of Experiments to Space Station (EXPRESS) rack. The rack system was recreated in a ground-test facility to test the MPU performances. The cultivation of a portion of green daikon microgreens was produced with the consumption of only 30 ml of nutrient solution and less than 7.5 kWh for up to 6 portion-sized cultivation. To proper design the system, particular focus was spent on the design of illumination subsystem. A simple but effective light distribution model was implemented in a Matlab® code to simulate light distribution over the cultivation surface, and proper select the lamps positioning. Furthermore two experimental trials with four species of microgreens (red and green mustard, Brassica juncea, red and green radish, Raphanus sativus ) and six different light spectra was performed, to increase the biomass and secondary metabolites accumulation. The best light was a combination of 40% red, 20% green and 40% blue wavelengths, achieving an increment in dry biomass from 20% to 100%, depending on the species. A non-destructive fluorometric method (using the Multiplex®) for the analysis of secondary metabolites was tested, showing good correlation coefficients in green radish for chlorophyll, in red radish for anthocyanins and in both for flavonols measured concentration. Finally to reduce resource utilization of MPU and recycle cultivation wastes two biodegradation processes were studied: insect and bacteria decomposition. A modular, high confined rearing module (the Growing Rearing Module (GRM)) was designed and tested, completing a full rearing cycle of Hermetia Illucens from egg to egg. Insects were fed with 800 g of microgreens cultivation wastes obtaining 44 g of fresh larvae, which can be used as a noble protein source for astronauts. Also the cultivation (cellulose substrate) and food wastes were recycled thanks to an anaerobic bacteria digestion, obtaining more than two litres of fertilizer from 60 g of Space Organic Waste (SOW). The fertilizer was tested in a green daikon cultivation cycle in the MPU showing no statistically significant effect on dry mass accumulation.
Il futuro dell’esplorazione umana dello spazio dipende dalla capacità di provvedere ai bisogni metabolici degli astronauti, riducendo al minimo la necessità di rifornimenti da Terra. Una delle sfide principali è proprio quella di ricreare le condizioni ideali per la sopravvivenza degli esseri umani fornendo aria, acqua, cibo e protezione dall’ambiente esterno. Questa sfida è stata affrontata sviluppando diverse tecnologie di supporto vitale, studiando la possibilità di introdurre organismi vivi all’interno del ciclo. Tra i differenti aspetti da considerare per la sopravvivenza umana uno dei più importanti è la qualità e i valori nutrizionali del cibo consumato dagli astronauti. In ambienti estremi, come Marte o la Luna, il consumo di alimenti di alta qualità e ricchi di nutrienti biodisponibili diventa fondamentale per la sopravvivenza e la salute della crew. Per affrontare questo problema un prototipo per la coltivazione autonoma di microgreens (MPU) è stato progettato, realizzato e testato a terra. Le microverdure possono essere utilizzate come un integratore alimentare fresco, ready-to-eat e di altissima qualità, grazie ai loro effetti benefici sul corpo umano: l’effetto antitumorale e la riduzione degli effetti dannosi dell’ambiente spaziale sul corpo umano. Il sistema è compatibile con lo standard payload rack a bordo della stazione spaziale internazionale, basando lo sviluppo sulle dimensioni del Mid-Deck Locker Equivalent (MLE) drawer, presente nell’EXPRESS rack. Il sistema complessivo del rack stato riprodotto in una facility per il test a terra, per poter valutare le performance del MPU. La coltivazione di una singola porzione di ravanello Green Daikon è stata prodotta consumando soltanto 30 ml di soluzione nutritiva e consumando meno di 7.5 kWh per sei moduli indipendenti. Per progettare al meglio il sistema è stata prestata molta attenzione all’impianto di illuminazione artificiale, sviluppando un semplice ma efficace modello matematico per la simulazione della distribuzione di luce sulla superficie di coltivazione. Questo modello è stato implementato in un codice Matlab®, ed è stato utilizzato per il corretto posizionamento delle lampade di coltivazione. Successivamente due trial sperimentali con quattro specie di microverdure (due ravanelli e due senapi) sono stati condotti per valutare l’effetto di diverse ricette di luce sul metabolismo primario e secondario delle piante coltivate. In questo modo è stato possibile stabilire quale ricetta di luce favorisse l’accumulo di biomassa (prima trial) e come fosse possibile effettuare il fine-tuning della ricetta migliore per stimolare l’accumulo di metaboliti secondari utili al consumo umano, quali antocianine e flavonoli. A completare il lavoro di efficientamento di processo un ulteriore passo è stato svolto per ridurre i consumi del sistema e utilizzare i rifiuti della coltivazione. In particolare, due processi di biodegradazione sono stati studiati: insetti e batteri anaerobici. Un sistema modulare (il GRM, Growing Rearing Module), ad alto livello di confinamento per l’allevamento di insetti è stato progettato, realizzato e testato con un ciclo completo di Hermetia Illucens, da uovo a uovo. Gli insetti sono stati nutriti con 800 g di rifiuti della coltivazione di microverdure (principalmente radici e parti inferiori dello stelo) ottenendo 44 g di larve fresche, che possono essere utilizzate come fonte di proteine nobili. Allo stesso modo i resti del tappeto di coltivazione delle microverdure sono stati degradati grazie ad una decomposizione batterica anerobica, ottenendo più di due litri di fertilizzante da 60 g di Space Organic Waste. Il fertilizzante così ottenuto è stato testato su una coltivazione di ravanello verde ottenendo nessun effetto significativo sull’accumulo di biomassa.
Microgreens production and biodegradation system to support future human space exploration
GAREGNANI, MARCO
2022/2023
Abstract
The future human exploration of space depends on the ability to provide for the metabolic needs of a crew, reducing the amount of re-supply required from Earth. One of the key-challenge is to recreate conditions suitable for human survival and well-being, providing water, food, air and shelter. This issue has been addressed by developing several types of Life Support System (LSS) over the years, studying the possibility to introduce biological entities in the loop. Among all the different aspects involving the human survival far from Earth, one of the most important is the quality and nutritional value of the food consumed by astronauts. In extreme environments, such as Moon, Mars or deep space, the consumption of high-quality, nutrient-rich and nutrient-bioavailable food becomes fundamental to the survival and well-being of the crew. To address this issue a prototype for the autonomous cultivation of microgreens, the Microgreens Production Unit (MPU) has been designed, assembled and ground-tested. Microgreens can be used as a fresh, ready-to-eat and healthy dietary supplement, thanks to their high nutritional quality and beneficial effects on human body, such as reducing risk of cancer and space-related effects. The system was designed to be compliant with International Space Station (ISS) standard payload rack, based on the Mid-Deck Locker Equivalent (MLE) drawer of the EXpedite the PRocessing of Experiments to Space Station (EXPRESS) rack. The rack system was recreated in a ground-test facility to test the MPU performances. The cultivation of a portion of green daikon microgreens was produced with the consumption of only 30 ml of nutrient solution and less than 7.5 kWh for up to 6 portion-sized cultivation. To proper design the system, particular focus was spent on the design of illumination subsystem. A simple but effective light distribution model was implemented in a Matlab® code to simulate light distribution over the cultivation surface, and proper select the lamps positioning. Furthermore two experimental trials with four species of microgreens (red and green mustard, Brassica juncea, red and green radish, Raphanus sativus ) and six different light spectra was performed, to increase the biomass and secondary metabolites accumulation. The best light was a combination of 40% red, 20% green and 40% blue wavelengths, achieving an increment in dry biomass from 20% to 100%, depending on the species. A non-destructive fluorometric method (using the Multiplex®) for the analysis of secondary metabolites was tested, showing good correlation coefficients in green radish for chlorophyll, in red radish for anthocyanins and in both for flavonols measured concentration. Finally to reduce resource utilization of MPU and recycle cultivation wastes two biodegradation processes were studied: insect and bacteria decomposition. A modular, high confined rearing module (the Growing Rearing Module (GRM)) was designed and tested, completing a full rearing cycle of Hermetia Illucens from egg to egg. Insects were fed with 800 g of microgreens cultivation wastes obtaining 44 g of fresh larvae, which can be used as a noble protein source for astronauts. Also the cultivation (cellulose substrate) and food wastes were recycled thanks to an anaerobic bacteria digestion, obtaining more than two litres of fertilizer from 60 g of Space Organic Waste (SOW). The fertilizer was tested in a green daikon cultivation cycle in the MPU showing no statistically significant effect on dry mass accumulation.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/208562