Bioregenerative Life Support Systems Research Articles

Beyond Earth: Harnessing Marine Resources for Sustainable Space Colonization

The quest for sustainable space exploration and colonization is a challenge in its infancy, which faces scarcity of resources and an inhospitable environment. In recent years, advancements in space biotechnology have emerged as potential solutions to the hurdles of prolonged space habitation. Taking cues from the oceans, this review focuses on the sundry types of marine organisms and marine-derived chemicals that have the potential of sustaining life beyond planet Earth. It addresses how marine life, including algae, invertebrates, and microorganisms, may be useful in bioregenerative life support systems, food production, pharmaceuticals, radiation shielding, energy sources, materials, and other applications in space habitats. With the considerable and still unexplored potential of Earth’s oceans that can be employed in developing space colonization, we allow ourselves to dream of the future where people can expand to other planets, not only surviving but prospering. Implementing the blend of marine and space sciences is a giant leap toward fulfilling man’s age-long desire of conquering and colonizing space, making it the final frontier.

Assessing black soldier fly pupation and survival in lunar regolith simulant: Implications for sustainable controlled habitats on the Moon

Bioregenerative life-support systems (BLSSs) will be crucial for extended space missions and extraterrestrial habitats. The black soldier fly, Hermetia illucens, is recognized for its efficient organic waste consumption, making it well-suited for closed environments like spacecraft. Our study assessed H. illucens adaptability to different substrates, including a lunar regolith simulant, pertinent to future lunar colonization. Remarkably resilient, H. illucens prepupal larvae successfully pupated in all tested substrates, but pupation timing varied, with no-substrate larvae pupating later. Pupal stage duration also differed, particularly with lunar regolith simulant and sand treatments resulting in longer durations. Substrate treatments significantly influenced the number of emerged adults, with lunar regolith simulant yielding more adults than the no-substrate treatment. Additionally, sand and wood shavings treatments produced more adults, highlighting H. illucens adaptability to various substrates, including lunar regolith. These findings are crucial for future BLSSs design. Additionally, H. illucens adaptability to lunar regolith provides insights into life's adaptability in space environments, guiding future experiments on celestial bodies. This study provides critical data on how different substrates, including lunar regolith simulants, influence H. illucens development and survival, advancing BLSSs and ecological science in both space and terrestrial contexts.

CAVITY RING DOWN SPECTROSCOPY AS A TOOL FOR MONOCHROMATIC LIGHT ACTION ON TOMATO PLANTS IN BIO-REGENERATIVE LIFE SUPPORT SYSTEMS

Narrow spectrum LEDs, which regulate diverse photo-morphogenetic responses of plants, can be used to achieve desired plant responses in terms of germination, growth rate, and productivity. Current study examined the effect of blue (465-475 nm), green (515-530 nm), red (620-630 nm), and cool-white light (CCT 6000-6500K) on tomato (Solanum lycopersicum) different cultivars, with determinate and indeterminate growth. Our findings show that monochromatic light had a substantial impact on germination, growth, hydration status, and δ13C values in plantlets grown under experimental conditions. When compared to the other wavelengths, red light stimulates the most and visible light inhibits the most germination in the selected tomato varieties. The lowest elongation was measured in visible light and the greatest elongation was measured in red light, resulting in a drop in the PPFD from 326.1 to 179.4 μmol∙m−2∙s−1. Our findings imply that the δ13C signature in plants detected by Cavity Ring Down Spectroscopy could be a useful proxy for quickly assessing the physiological condition of plantlets in their early stages of development in Bio-Regenerative Life Support Systems.

Synechococcus sp. PCC7335 responses to far-red enriched spectra and anoxic/microoxic atmospheres: Potential for astrobiotechnological applications

Recently, cyanobacteria have gained attention in space exploration to support long-term crewed missions via Bioregenerative Life Support Systems. In this frame, cyanobacteria would provide biomass and profitable biomolecules through oxygenic photosynthesis, uptaking CO2, and releasing breathable O2. Their growth potential and organic matter production will depend on their ability to photoacclimate to different light intensities and spectra, maximizing incident light harvesting. Studying cyanobacteria responses to different light regimes will also benefit the broader field of astrobiology, providing data on the possibility of oxygenic photosynthetic life on planets orbiting stars with emission spectra different than the Sun. Here, we tested the acclimation and productivity of Synechococcus sp. PCC7335 (hereafter PCC7335), capable of Far-Red Light Photoacclimation (FaRLiP) and type III chromatic acclimation (CA3), in an anoxic, CO2-enriched atmosphere and under a spectrum simulating the low energetic light regime of an M-dwarf star, also comparable to a subsuperficial environment. When exposed to the light spectrum, with few photons in the visible (VIS) and rich in far-red (FR), PCC7335 did not activate FaRLiP but acclimated only via CA3, achieving a biomass productivity higher than expected, considering the low VIS light availability, and a higher production of phycocyanin, a valuable pigment, with respect to solar light. Its growth or physiological responses of PCC7335 were not affected by the anoxic atmosphere. In these conditions, PCC7335 efficiently produced O2 and scavenged CO2. Results highlight the photosynthetic plasticity of PCC7335, its suitability for astrobiotechnological applications, and the importance to investigate biodiversity of oxygenic photosynthesis for searching life beyond Earth.

Extremophiles in Space Exploration.

In the era of deep space exploration, extremophile research represents a key area of research w.r.t space survival. This review thus delves into the intriguing realm of 'Space and Astro Microbiology', providing insights into microbial survival, resilience, and behavioral adaptations in space-like environments. This discussion encompasses the modified behavior of extremophilic microorganisms, influencing virulence, stress resistance, and gene expression. It then shifts to recent studies on the International Space Station and simulated microgravity, revealing microbial responses that impact drug susceptibility, antibiotic resistance, and its commercial implications. The review then transitions into Astro microbiology, exploring the possibilities of interplanetary transit, lithopanspermia, and terraforming. Debates on life's origin and recent Martian meteorite discoveries are noted. We also discuss Proactive Inoculation Protocols for selecting adaptable microorganisms as terraforming pioneers. The discussion concludes with a note on microbes' role as bioengineers in bioregenerative life support systems, in recycling organic waste for sustainable space travel; and in promoting optimal plant growth to prepare Martian and lunar basalt. This piece emphasizes the transformative impact of microbes on the future of space exploration.

Importance and challenges of integrating BLSS into ECLSS

Bioregenerative Life Support Systems (BLSS) are a key facet of plans for long term habitats on other celestial bodies. With the Artemis program headed to the moon and SpaceX pushing towards Mars the roadmap is about 10–20 years. Therefore it is vital to consider how BLSS will work with the traditional physicochemical Environmental Control and Life Support Systems (ECLSS). Biological systems are complicated. Their inputs and outputs cannot be turned on and off the way physicochemical systems can. Therefore the accurate monitoring and prediction of these systems is fundamental to integrating the BLSS into the life support system as a whole. This paper will summarize the history of BLSS research, the system requirements for integrating a BLSS into the ECLSS, and the research needed to meet these requirements. As the world looks towards the future of humans living on other celestial bodies, there is a lot of work to do to support keeping them safe and healthy. Bioregenerative Life Support Systems have potential to provide massive support, if they are effectively integrated with the physicochemical systems.

Assessment of Fertility Dynamics and Nutritional Quality of Potato Tubers in a Compost-Amended Mars Regolith Simulant.

Mars exploration will foresee the design of bioregenerative life support systems (BLSSs), in which the use/recycle of in situ resources might allow the production of food crops. However, cultivation on the poorly-fertile Mars regolith will be very challenging. To pursue this goal, we grew potato (Solanum tuberosum L.) plants on the MMS-1 Mojave Mars regolith simulant, pure (R100) and mixed with green compost at 30% (R70C30), in a pot in a cold glasshouse with fertigation. For comparison purposes, we also grew plants on a fluvial sand, pure (S100) and amended with 30% of compost (S70C30), a volcanic soil (VS) and a red soil (RS). We studied the fertility dynamics in the substrates over time and the tuber nutritional quality. We investigated nutrient bioavailability and fertility indicators in the substrates and the quality of potato tubers. Plants completed the life cycle on R100 and produced scarce but nutritious tubers, despite many critical simulant properties. The compost supply enhanced the MMS-1 chemical/physical fertility and determined a higher tuber yield of better nutritional quality. This study demonstrated that a compost-amended Mars simulant could be a proper substrate to produce food crops in BLSSs, enabling it to provide similar ecosystem services of the studied terrestrial soils.

Non-destructive real-time analysis of plant metabolite accumulation in radish microgreens under different LED light recipes.

The future of human space missions relies on the ability to provide adequate food resources for astronauts and also to reduce stress due to the environment (microgravity and cosmic radiation). In this context, microgreens have been proposed for the astronaut diet because of their fast-growing time and their high levels of bioactive compounds and nutrients (vitamins, antioxidants, minerals, etc.), which are even higher than mature plants, and are usually consumed as ready-to-eat vegetables. Our study aimed to identify the best light recipe for the soilless cultivation of two cultivars of radish microgreens (Raphanus sativus, green daikon, and rioja improved) harvested eight days after sowing that could be used for space farming. The effects on plant metabolism of three different light emitting diodes (LED) light recipes (L1-20% red, 20% green, 60% blue; L2-40% red, 20% green, 40% blue; L3-60% red, 20% green, 20% blue) were tested on radish microgreens hydroponically grown. A fluorimetric-based technique was used for a real-time non-destructive screening to characterize plant methabolism. The adopted sensors allowed us to quantitatively estimate the fluorescence of flavonols, anthocyanins, and chlorophyll via specific indices verified by standardized spectrophotometric methods. To assess plant growth, morphometric parameters (fresh and dry weight, cotyledon area and weight, hypocotyl length) were analyzed. We observed a statistically significant positive effect on biomass accumulation and productivity for both cultivars grown under the same light recipe (40% blue, 20% green, 40% red). We further investigated how the addition of UV and/or far-red LED lights could have a positive effect on plant metabolite accumulation (anthocyanins and flavonols). These results can help design plant-based bioregenerative life-support systems for long-duration human space exploration, by integrating fluorescence-based non-destructive techniques to monitor the accumulation of metabolites with nutraceutical properties in soilless cultivated microgreens.

Microbial products for space nutrition

Sustainably producing nutrients beyond Earth is one of the biggest technical challenges for future extended human space missions. Microorganisms such as microalgae and cyanobacteria can provide astronauts with nutrients, pharmaceuticals, pure oxygen, and bio-based polymers, making them an interesting resource for constructing a circular bioregenerative life support system in space.

Effects of altered gravity on growth and morphology in Wolffia globosa implications for bioregenerative life support systems and space-based agriculture

Understanding the response of plants to varied gravitational conditions is vital for developing effective food production in space bioregenerative life support systems. This study examines the impact of altered gravity conditions on the growth and morphological responses of Wolffia globosa (commonly known as “water lentils” or “duckweed”), assessing its potential as a space crop. Although an experiment testing the effect of simulated microgravity on Wolffia globosa has been previously conducted, for the first time, we investigated the effect of multiple gravity levels on the growth and morphological traits of Wolffia globosa plants. The plant responses to simulated microgravity, simulated partial gravity (Moon), and hypergravity environments were evaluated using random positioning machines and the large-diameter centrifuge. As hypothesized, we observed a slight reaction to different gravitational levels in the growth and morphological traits of Wolffia globosa. The relative growth rates (RGR) of plants subjected to simulated microgravity and partial gravity were reduced when compared to those in other gravity levels. The morphological analysis revealed differences in plant dimensions and frond length-to-width ratios under diverse gravity conditions. Our findings showed that Wolffia globosa is responsive to gravitational changes, with its growth and morphological adaptations being slightly influenced by varying gravitational environments. As for other crop species, growth was reduced by the microgravity conditions; however, RGR remained substantial at 0.33 a day. In conclusion, this study underscores the potential of Wolffia globosa as a space crop and its adaptability to diverse gravitational conditions, contributing to the development of sustainable food production and bioregenerative life support systems for future space exploration missions.

Soil-like substrate fertility restoration method in bioregenerative life support systems

The research focused on chard plants grown in a vegetation chamber under irradiation of 600 μmol/(m2s-1) FAR and elevated CO2 concentration in the range of 1500-2000 ppm. The objective is to determine the feasibility of incorporating gaseous nitrogen-containing products of physicochemical mineralization of human exometabolites into the cycling process in relation to the conditions of bioregenerative systems of human life support. To replenish the Impoverished soil-like substrate with available forms of nitrogen, we introduced NH4NO3 into the irrigation solution. This can be obtained from NH3, which is a part of gaseous intrasystem mass exchange products. The incorporation of NH3 into the intrasystem cycle comprised three main steps. 1) Some of the NH3 was oxidized to nitrogen oxides, which dissolved in water and formed acid solutions; 2) Another part of the NH3 was barbotaged through a nitric acid solution to obtain NH4NO3; 3) The obtained ammonium salts were used as fertilizer and added to the irrigation solution for the cultivation of chard plants, which represent the phototrophic link in the bioregenerative life support system. The results clearly demonstrated that replenishing the available nitrogen forms in the Impoverished soil-like substrate to match the original substrate levels resulted in plant mass comparable to that of plants grown on freshly prepared substrate. The research results prove the potential of the developed technologies for involving dead-end gaseous nitrogen-containing waste from human activity in the intrasystem mass exchange of the life-support system.

Thriving on Mars: Potatoes as the Answer to Martian Challenges

Humans have committed themselves to the exploration of space and the quest for a habitable planet. Central to the development of a sustainable ecosystem that can provide essential resources like food and water is the implementation of space plant cultivation systems. In the pursuit of bio-regenerative life support systems for human space exploration, the inclusion of plants is imperative. This study focuses on assessing potential challenges associated with cultivating Potatoes (Solanum tuberosum) under simulated Martian conditions. Potatoes exhibit adaptability to extremely cold and dry environments, making them a promising candidate for extraterrestrial agriculture. The advantages of potatoes include their high yield, rich content of easily digestible carbohydrates, elevated protein levels, and simplicity of propagation. When induced to tuberize, potatoes can achieve a harvest index exceeding 80%, approximately double that of traditional grain crops. Notably, unlike certain crops such as soybeans and certain grains, potatoes do not necessitate elaborate processing procedures before consumption. The Potato, specifically varieties like Norland, Denali, and Russet Burbank, has garnered attention in research funded by the US National Aeronautics and Space Administration (NASA). Tests have revealed that these cultivars can successfully undergo tuberization even under constant bright light conditions, emphasizing their potential suitability for life support functions in space exploration contexts

Modelling physical processes in higher plants using leaf replicas for space applications

In the future, higher plant cultivation will be a key component of Bioregenerative Life-Support Systems. This will require a deep understanding of phenomena that play an important role at the core of plant metabolism and of their interaction with the environment. Plants are complex organisms that must be studied with the use of leaf replicas. This enables the study of physical phenomena at the leaf surface, without biochemical or biological interactions nor genetic variability. To assess the influence of gravity, it is a necessary step to develop precise mechanistic models of plant behaviour in space. This review article presents the state-of-the-art of leaf replicas and concomitant phenomena, with a space gaze.

Phosphorus-solubilizing bacteria improve the growth of Nicotiana benthamiana on lunar regolith simulant by dissociating insoluble inorganic phosphorus

In-situ utilization of lunar soil resources will effectively improve the self-sufficiency of bioregenerative life support systems for future lunar bases. Therefore, we have explored the microbiological method to transform lunar soil into a substrate for plant cultivation. In this study, five species of phosphorus-solubilizing bacteria are used as test strains, and a 21-day bio-improving experiment with another 24-day Nicotiana benthamiana cultivation experiment are carried out on lunar regolith simulant. We have observed that the phosphorus-solublizing bacteria Bacillus mucilaginosus, Bacillus megaterium, and Pseudomonas fluorescens can tolerate the lunar regolith simulant conditions and dissociate the insoluble phosphorus from the regolith simulant. The phosphorus-solubilizing bacteria treatment improves the available phosphorus content of the regolith simulant, promoting the growth of Nicotiana benthamiana. Here we demonstrate that the phosphorus-solubilizing bacteria can effectively improve the fertility of lunar regolith simulant, making it a good cultivation substrate for higher plants. The results can lay a technical foundation for plant cultivation based on lunar regolith resources in future lunar bases.

Evidence of Potential Organo-Mineral Interactions during the First Stage of Mars Terraforming

Future space missions to Mars will depend on the development of bioregenerative life support systems. Mars regolith contains most of the nutrients needed for plant growth, but not organic matter (OM). Although Mars simulants have been deeply characterized and tested as growing media, no data are available about their possible modification occurring during terraforming, including the interaction of exogeneous OM with iron (Fe) oxides, particularly abundant in Mars regolith. The aim of this study was to investigate the mineral transformation and the OM evolution occurring in the early stages of the terraforming process. Potato was grown for 99 days on Mojave Mars Simulant MMS-1, alone (R100) and mixed with a compost 70:30 v:v (R70C30), and on a fluvial sand, alone (S100) and mixed with compost (S70C30), for comparison. Bulk (BK) and potato tubero/rhizo-sphere (RH) soils were fractionated to obtain particulate OM (POM) and mineral-associated OM (MAOM). Bulk samples and corresponding fractions were characterized for total nitrogen and organic carbon (C) and analyzed by Fe K-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy. Organic C increased by 10 and 25 times in S70C30 and R70C30, respectively, compared to S100 and R100. Most of the organic C accumulated in the POM fraction of both growing substrates, while its content in the MAOM was 3 times higher in R70C30 than in S70C30. No significant differences between BK and RH were found. Finally, ferrihydrite mediated exogenous OM stabilization in regolith-based substrates, while Fe(III)-OM complexes were detected exclusively in sand-based growing media. Understanding mechanisms and testing potential sustainable practices for creating Mars regolith similar to terrestrial soil will be fundamental to sustain food crop production on Mars.

The first biological experiment on lunar surface for Humankind: Device and results

The Bioregenerative Life Support System (BLSS) is an indispensable part of extraterrestrial bases as it can provide sufficient food, fresh air, recycle waste, and create a safe environment for humans. However, it is still uncertain how the natural environment of extraterrestrial bodies would affect the function of an artificial ecosystem like BLSS. The Chinese Chang'e 4 lunar lander carried a micro-ecosystem called Biological Experiment Payload (BEP), developed by Chongqing University, and conducted the first biological experiments for humans on the back of the Moon to assess the effects of low gravity, intense radiation, and light on the lunar surface to living things. The payload weighs 2.608 kg, with 198 mm in height and 173 mm in diameter, offering a total inside space of 0.82L, containing 0.42L of bio-activity space. Cotton seeds, Potato seeds, Arabidopsis seeds, Rape seeds, Fly eggs, Yeast, and 18 ml of water were placed in the BEP, which was kept at a constant atmospheric pressure. Through a light guide tube, sunlight from the lunar surface can enter the payload's interior, allowing plants to photosynthesize. One remarkable feature of BEP was the gap in radiation protection design.On January 3, 2019, BEP arrived on the back of the Moon and conducted an experiment lasting eight days, 22 h, and 45 min (Earth Day) during the first lunar day after landing. After 22 h of watering, the CCD camera captured cotton seed germination, compared to 53 h after watering in the ground synchronization experiment. The cotton seedling on the lunar surface showed a faster germination rate than the simultaneous experiments on the ground. Also, the morphology of the cotton on the Moon was changed, with its stem growing curved, developing a long part close to the substrate and a short upright portion while forming fat-flowing nodes close to the substrate. Finally, the leaves were also curled and did not unfold. The payload was dormant from 12 to 31 January 2019, with its interior remaining dark and temperatures reaching as low as −52 °C. After the lunar night, the leaves of the terrestrial synchronous experiment were completely blackened and in pieces, in contrast to the Seedling on the Moon, which was upright and green. This experiment demonstrated that plants could grow on the lunar surface even in intense radiation, low gravity (1/6 g), and prolonged intense light. It was also the first time that a biological experiment was carried out by humans on the Moon using sunlight from space to power photosynthesis.

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

Bioregenerative life support systems (BLSS) are vital for long-duration and remote space missions to increase mission sustainability. These systems break down human waste materials into nutrients and CO2 for plants and other edible organisms, which in turn provide food, fresh water, and oxygen for astronauts. The central idea is to create a materially closed loop, which can significantly reduce mission mass and volume by cutting down or even eliminating disposable waste. In most BLSS studies only a fraction of the resources, such as food, are provided by the system itself, with the rest taken on board at departure or provided through resupply missions. However, for autonomous long-duration space missions without any possibility of resupply, a BLSS that generates all resources with minimal or no material loss, is essential. The goal of this study is to develop a stoichiometric model of a conceptually fully closed BLSS that provides all the metabolic needs of the crew and organisms. The MELiSSA concept of the European Space Agency is used as reference system, consisting of five interconnected compartments, each inhabited by different types of organisms. A detailed review of publicly available MELiSSA literature from 1989 to 2022 revealed that no existing stoichiometric model met the study’s requirements. Therefore, a new stoichiometric model was developed to describe the cycling of the elements C, H, O, and N through all five MELiSSA compartments and one auxiliary compartment. A compact set of chemical equations with fixed coefficients was established for this purpose. A spreadsheet model simulates the flow of all relevant compounds for a crew of six. By balancing the dimensions of the different compartments, a high degree of closure is attained at steady state, with 12 out of 14 compounds exhibiting zero loss, and oxygen and CO2 displaying only minor losses between iterations. This is the first stoichiometric model of a MELiSSA-inspired BLSS that describes a continuous provision of 100% of the food and oxygen needs of the crew. The stoichiometry serves as the foundation of an agent-based model of the MELiSSA loop, as part of the Evolving Asteroid Starships (E|A|S) research project.

From urine to food and oxygen: effects of high and low NH4+:NO3- ratio on lettuce cultivated in a gas-tight hydroponic facility.

In situ production of food, water and oxygen is essential for long-duration human space missions. Higher plants represent a key element in Bioregenerative Life Support Systems (BLSS), where crop cultivation can be based on water and nutrients recovered from waste and wastewater. Human urine exemplifies an important waste stream with potential to provide crops with nitrogen (N) and other nutrients. Dynamic waste composition and treatment processes may result in mineralized fractions with varying ammonium (NH4 +) to nitrate (NO3 -) ratios. In this study, lettuce was cultivated in the unique ESA MELiSSA Plant Characterization Unit, an advanced, gas-tight hydroponic research facility offering controlled environment and continuous monitoring of atmospheric gas composition. To evaluate biological and system effects of nutrient solution NH4 +:NO3 - ratio, two crop tests were run with different NH4 + to total N ratio (NH4 +:N) and elevated concentrations of Na+ and Cl- in line with a urine recycling scenario. Plants cultivated at 0.5 mol·mol-1 NH4 +:N (HiNH4 +) achieved 50% lower shoot biomass compared to those cultivated at 0.1 mol·mol-1 NH4 +:N (LoNH4 +), accompanied by higher shoot dry weight content and lower harvest index. Analyses of projected leaf area over time indicated that the reduced biomass observed at harvest could be attributed to a lower specific growth rate during the close-to-exponential growth phase. The HiNH4 + crop produced 40% less O2 over the full cultivation period. However, normalization of the results indicated a marginal increase in O2 production per time and per projected leaf area for the HiNH4 + crop during the exponential growth phase, in line with a higher shoot chlorophyll content. Mineral analysis demonstrated that the biomass content of NH4 + and NO3 - varied in line with the nutrient solution composition. The ratio of consumed NH4 + to consumed N was higher than the NH4 +:N ratio of the nutrient solution for both crop tests, resulting in decreasing NH4 +:N ratios in the nutrient solution over time. The results provide enhanced insight for design of waste processes and crop cultivation to optimize overall BLSS efficiency and hold valuable potential for improved resource utilization also in terrestrial food production systems.

Assessment of batch culture conditions for cyanobacterial propagation for a bioreactor in space

One important point in human space exploration is the reliable air, water and food production for the space crew, less dependent from cargo supply. Bioregenerative life support systems aim to overcome this challenge. The life support program MELiSSA of the European Space Agency uses the cyanobacterium Limnospira indica for air revitalization and food production. In the Space flight experiments ArtEMISS-B and -C, L. indica is tested on the International Space Station. In this study we elucidate which conditions are most favorable for cell propagation from inoculum to a full culture in space to enable a high final biomass concentration, with high pigment composition for an efficient bioprocess. We found that lower light intensities (36–75 µmol photons m-2 s-1) show higher maximum biomass densities and higher pigment contents than cultures grown above 100 µmol photons m-2 s-1. 36 μmol photons m-2 s-1 resulted in maximum biomass concentrations of 3.36 ± 0.15 g L-1 (23 °C), while cultures grown at 140 µmol photons m-2 s-1 only achieved concentrations of 0.82 ± 0.10 g L-1 (25°C) (−75.8%). Colder temperatures (21°C–25°C) showed a negative effect on the pigment content. At 36 µmol photons m-2 s-1, a temperature of 30°C gave a phycocyanin concentration of 0.122 ± 0.014 g g DW-1 and 23°C resulted in 0.030 ± 0.003 g g DW-1 (−75.4%). In conclusion, a low light intensity (36–80 µmol photons m-2 s-1) in combination with warm temperature (30°C–34°C) is optimal to obtain cultures with high pigment contents and high biomass concentrations in a batch culture.

Positive mood-related gut microbiota in a long-term closed environment: a multiomics study based on the “Lunar Palace 365” experiment

BackgroundPsychological health risk is one of the most severe and complex risks in manned deep-space exploration and long-term closed environments. Recently, with the in-depth research of the microbiota–gut–brain axis, gut microbiota has been considered a new approach to maintain and improve psychological health. However, the correlation between gut microbiota and psychological changes inside long-term closed environments is still poorly understood. Herein, we used the “Lunar Palace 365” mission, a 1-year-long isolation study in the Lunar Palace 1 (a closed manned Bioregenerative Life Support System facility with excellent performance), to investigate the correlation between gut microbiota and psychological changes, in order to find some new potential psychobiotics to maintain and improve the psychological health of crew members.ResultsWe report some altered gut microbiota that were associated with psychological changes in the long-term closed environment. Four potential psychobiotics (Bacteroides uniformis, Roseburia inulinivorans, Eubacterium rectale, and Faecalibacterium prausnitzii) were identified. On the basis of metagenomic, metaproteomic, and metabolomic analyses, the four potential psychobiotics improved mood mainly through three pathways related to nervous system functions: first, by fermenting dietary fibers, they may produce short-chain fatty acids, such as butyric and propionic acids; second, they may regulate amino acid metabolism pathways of aspartic acid, glutamic acid, tryptophan, etc. (e.g., converting glutamic acid to gamma–aminobutyric acid; converting tryptophan to serotonin, kynurenic acid, or tryptamine); and third, they may regulate other pathways, such as taurine and cortisol metabolism. Furthermore, the results of animal experiments confirmed the positive regulatory effect and mechanism of these potential psychobiotics on mood.ConclusionsThese observations reveal that gut microbiota contributed to a robust effect on the maintenance and improvement of mental health in a long-term closed environment. Our findings represent a key step towards a better understanding the role of the gut microbiome in mammalian mental health during space flight and provide a basis for future efforts to develop microbiota-based countermeasures that mitigate risks to crew mental health during future long-term human space expeditions on the moon or Mars. This study also provides an essential reference for future applications of psychobiotics to neuropsychiatric treatments.3wJ6S91ppJCbbcXcW_ZHEyVideo