Results for “Space Algae”

NASA NTRSDate not supplied

Space Algae: Understanding the Genomic Impacts on Microalgae After Growth in the International Space Station

Plants and microbes can be used for biological support of crewed space missions. The radiation and microgravity environment of spaceflight is expected to increase genetic mutation of all organisms. It is essential to understand how spaceflight impacts mutation rates in photosynthetic organisms to enable appropriate countermeasures and ensure productivity during long duration and deep space missions. The Space Algae flight experiments to the International Space Station (ISS) are studying the genomic stability of microalgae that could potentially be used in biological life support systems. Space Algae-1 grew ultraviolet light mutagenized Chlamydomonas reinhardtii in the VEGGIE plant growth chamber for approximately 40 mitotic generations over one month on the ISS. Whole genome sequencing from pooled cell samples every 10 generations revealed that spaceflight cultures had an ~50% increase in DNA polymorphisms relative to ground controls. These mutations had a novel base substitution signature and suggested a risk that microalgae may be unstable for long-term production in space. Space Algae-2 is focusing on the edible cyanobacterium Arthrospira platensis, commonly known as Spirulina. This experiment seeks to grow serial cultures to allow the organism to evolve in long-term spaceflight. Biological responses of the cells to spaceflight will be assessed with multi-omics analyses to determine mutation load, gene/protein expression, metabolic/nutritional composition, and cell morphology.

Algae↗

NASA NTRSDate not supplied

Space Algae: Understanding the Genomic Impacts on Microalgae After Growth in the International Space Station

Plants and microbes can be used for biological support of crewed space missions. The radiation and microgravity environment of spaceflight is expected to increase genetic mutation of all organisms. It is essential to understand how spaceflight impacts mutation rates in photosynthetic organisms to enable appropriate countermeasures and ensure productivity during long duration and deep space missions. The Space Algae flight experiments to the International Space Station (ISS) are studying the genomic stability of microalgae that could potentially be used in biological life support systems. Space Algae-1 grew ultraviolet light mutagenized Chlamydomonas reinhardtii in the VEGGIE plant growth chamber for approximately 40 mitotic generations over one month on the ISS. Whole genome sequencing from pooled cell samples every 10 generations revealed that spaceflight cultures had an ~50% increase in DNA polymorphisms relative to ground controls. These mutations had a novel base substitution signature and suggested a risk that microalgae may be unstable for long-term production in space. Space Algae-2 is focusing on the edible cyanobacterium Arthrospira platensis, commonly known as Spirulina. This experiment seeks to grow serial cultures to allow the organism to evolve in long-term spaceflight. Biological responses of the cells to spaceflight will be assessed with multi-omics analyses to determine mutation load, gene/protein expression, metabolic/nutritional composition, and cell morphology.

Algae↗

NASA NTRSDate not supplied

Testing A Concept of Operations for the Space Algae-2 Spaceflight Experiment

Algae has abundant potential spaceflight applications to enable future crewed missions and habitation beyond low-Earth orbit, including production of essential nutrients, oxygen, and biofuels. Implementing algae production in space requires understanding how different algae species respond to spaceflight stressors such as microgravity and radiation over a realistic production time course. Space Algae-2 is focusing on Arthrospira platensis, a filamentous cyanobacteria commonly known as Spirulina. A. platensis is a human nutritional supplement on Earth that is a good source of essential amino acids, β-carotene, thiamin, riboflavin, and antioxidants. The Space Algae-2 experiment plans to grow and passage A. platensis continuously aboard the International Space Station for six months. The algae produced will be analyzed with multi-omics profiling to monitor for genetic and phenotype stability in the spaceflight environment. This presentation will report the results from pre-flight science verification tests of the concept of operations for Space Algae-2. The purpose of these tests was to determine if the proposed crew operations for serial passages, sample collection, and sample preservation are feasible to meet science requirements for axenic culturing and preservation of DNA, RNA, protein, and nutritional metabolites.

Microalgae↗

NASA NTRSDate not supplied

Space Algae-2 Ground and Lunar Analog Studies in Preparation for Long-Duration Propagation of Cyanobacteria in Spaceflight

There are numerous applications for microalgae in spaceflight missions and on Earth, such as, oxygen production, carbon dioxide removal, nutrition, wastewater processing, and biofuel production. Space Algae-2 aims to test the genetic stability of Arthrospira platensis, commonly known as spirulina, during six-months of continuous culture in spaceflight on the International Space Station. Long-duration exposure to ionizing radiation and microgravity may impact growth, nutrient composition, and genetic stability. The high protein, vitamin, antioxidant content, and radiation resistance make spirulina a promising candidate for bioregenerative life support systems during long-duration missions. A concept of operations was developed to grow and harvest algal biomass in space. Preflight testing experiments were conducted to optimize conditions for an extended growth period in a gas permeable bioreactor bag. Preflight and post-harvest storage methods were developed in addition to a novel cryopreservation method. After sample return, multi-omics analysis will be conducted to determine the mutation rate, gene expression, and protein and metabolite profile. The concept of operations for Space Algae-2 was tested at HI-SEAS (Hawai’i Space Exploration Analog and Simulation) during a six-day lunar analog mission (EMMIHS23, EuroMoonMars, International MoonBase Alliance, HI-SEAS, 2023). A. platensis was grown in the semi-controlled environment using flight-like hardware and solar powered LED lights. Then, the biomass was harvested and used to supplement bread as an example of A. platensis utilization. Overall, the data collected from Space Algae-2 will inform potential bioengineering of spirulina for space and terrestrial applications.

Algae↗

NASA NTRSDate not supplied

Space Algae-2 Ground and Lunar Analog Studies in Preparation for Long-Duration Propagation of Cyanobacteria in Spaceflight

There are numerous applications for microalgae in spaceflight missions and on Earth, such as oxygen production, carbon dioxide removal, nutrition, wastewater processing, and biofuel production. Space Algae-2 aims to test the genetic stability of Arthrospira platensis, commonly known as spirulina, during six-months of continuous culture on the International Space Station. Long-duration exposure to ionizing radiation and microgravity may impact growth, nutrient composition, and genetic stability. The high protein, vitamin, antioxidant content, and radiation resistance make spirulina a promising candidate for bioregenerative life support systems. A concept of operations was developed to grow and harvest algal biomass in space. Preflight testing experiments optimized conditions for an extended growth period in a gas permeable bioreactor bag. Preflight and post-harvest storage methods were developed in addition to a novel cryopreservation method. After sample return, multi-omics analysis will be conducted to determine the mutation rate, gene expression, and the protein and metabolite profile. The concept of operations for Space Algae-2 was tested during a lunar mission simulation within a semi-controlled environment. During a six-day lunar analog mission at the Hawai’i Space Exploration Analog and Simulation (HI-SEAS) A. platensis was successfully grown using flight-like hardware. The cyanobacteria were harvested and used to supplement bread as an example of spirulina biomass utilization. Overall, the data collected from Space Algae-2 will inform potential bioengineering of spirulina for space and terrestrial applications.

Algae↗

NASA NTRS2024

Space Algae-2 Ground and Lunar Analog Studies in Preparation for Long-Duration Propagation of Cyanobacteria in Spaceflight

There are numerous applications for microalgae in spaceflight missions and on Earth, such as oxygen production, carbon dioxide removal, nutrition, wastewater processing, and biofuel production. Space Algae-2 aims to test the genetic stability of Arthrospira platensis, commonly known as spirulina, during six-months of continuous culture on the International Space Station. Long-duration exposure to ionizing radiation and microgravity may impact growth, nutrient composition, and genetic stability. The high protein, vitamin, antioxidant content, and radiation resistance make spirulina a promising candidate for bioregenerative life support systems. A concept of operations was developed to grow and harvest algal biomass in space. Preflight testing experiments optimized conditions for an extended growth period in a gas permeable bioreactor bag. Preflight and post-harvest storage methods were developed in addition to a novel cryopreservation method. After sample return, multi-omics analysis will be conducted to determine the mutation rate, gene expression, and the protein and metabolite profile. The concept of operations for Space Algae-2 was tested during a lunar mission simulation within a semi-controlled environment. During a six-day lunar analog mission at the Hawai’i Space Exploration Analog and Simulation (HI-SEAS) A. platensis was successfully grown using flight-like hardware. The cyanobacteria were harvested and used to supplement bread as an example of spirulina biomass utilization. Overall, the data collected from Space Algae-2 will inform potential bioengineering of spirulina for space and terrestrial applications.

Algae↗

NASA NTRSDate not supplied

Space Algae-2: Preflight Testing for A Long-Duration, Multi-Omics Analysis of Arthrospira Platensis

The cyanobacteria Arthrospira platensis NIES-39, commonly known as spirulina, could provide a fresh supply of nutrients for crew on long-duration spaceflight missions. Spirulina is a readily digestible food that is high in protein with all essential amino acids as well as significant levels of B vitamins, antioxidants, and anti-inflammatory metabolites. Spaceflight has multiple abiotic stressors such as increased ionizing radiation and microgravity, which causes a lack of convective mixing. These environmental conditions may impact productivity, nutritional composition, and in long-duration propagation, spaceflight stress may impact the genetic stability of spirulina cultures. We are developing an International Space Station experiment to continuously culture A. platensis for six months. Multi-omics profiling will be used to monitor for changes in the genome, transcriptome, proteome, and metabolome to determine if A. platensis is a suitable nutritional supplement on long-duration missions. During preflight testing we developed a protocol for inoculated liquid cultures to survive a 10-week storage period prior to photo-incubation. The bioreactor bag, temperature, and lighting conditions that support a 14-day growth cycle between passages were also determined. Media testing identified minimal salts supporting robust growth that can be stored in liquid or dry form. A simple filtration method was developed to dewater cultures and harvest biomass for frozen sample return. We optimized a cryopreservation method to enable return of live cells for isolation of individual A. platensis clones. The concept of operations for Space Algae-2 developed from these test results as well as progress on multi-omics analysis methods will be presented.

Algae↗

NASA NTRSDate not supplied

Space Algae-2: Preflight Testing for A Long-Duration, Multi-Omics Analysis of Arthrospira Platensis

The cyanobacteria Arthrospira platensis NIES-39, commonly known as spirulina, could provide a fresh supply of nutrients for crew on long-duration spaceflight missions. Spirulina is a readily digestible food that is high in protein with all essential amino acids as well as significant levels of B vitamins, antioxidants, and anti-inflammatory metabolites. Spaceflight has multiple abiotic stressors such as increased ionizing radiation and microgravity, which causes a lack of convective mixing. These environmental conditions may impact productivity, nutritional composition, and in long-duration propagation, spaceflight stress may impact the genetic stability of spirulina cultures. We are developing an International Space Station experiment to continuously culture A. platensis for six months. Multi-omics profiling will be used to monitor for changes in the genome, transcriptome, proteome, and metabolome to determine if A. platensis is a suitable nutritional supplement on long-duration missions. During preflight testing we developed a protocol for inoculated liquid cultures to survive a 10-week storage period prior to photo-incubation. The bioreactor bag, temperature, and lighting conditions that support a 14-day growth cycle between passages were also determined. Media testing identified minimal salts supporting robust growth that can be stored in liquid or dry form. A simple filtration method was developed to dewater cultures and harvest biomass for frozen sample return. We optimized a cryopreservation method to enable return of live cells for isolation of individual A. platensis clones. The concept of operations for Space Algae-2 developed from these test results as well as progress on multi-omics analysis methods will be presented.

Algae↗

NASA NTRSDate not supplied

Benchmarking Computational Tools for Calling SNPs and Indels in Complex Microbial Populations

The NASA BioNutrients missions seek to understand the suitability of microorganisms for bioproduction during space flight. One topic of interest is the stability of microbial genomes during long-term ambient storage and subsequent rehydration and growth. To address these questions, samples from 8 species were flown to ISS for 5 years of desiccated storage at ambient temperature (Stasis Packs) and 2 species were packaged along with powdered media inside a bioreactor system to allow hydration and growth in microgravity (Production Packs). For both systems, Whole Genome Sequencing (WGS) of the DNA extracted from the returned samples and paired ground controls will be conducted to identify changes in genome stability due to time, storage conditions and growth in space. Across the technical replicates, ground controls, 10 timepoints, and multiple experimental conditions, ~300 samples have been selected for initial analysis with WGS sequencing to 100x coverage. A flexible and resource efficient mutation calling pipeline is needed to process this large dataset and allow for comparisons between species. Many bioinformatics tools for calling Indels and Single Nucleotide Variants (SNVs) are designed for use with pure isolates, where true variations from the reference genome are expected to dominate the reads aligning to the location of mutation. In contrast, DNA from the Stasis Pack (SP) samples was collected directly after recovery from desiccated storage and the Production Pack (PP) samples were collected after fermentation. In this context, reads with mutations are expected to be less frequent than reads that align with the reference genome, as each sample will include multiple lines of cells. Thus, BioNutrients samples are expected to be similar to samples from cancer cell or “pooled” sequencing approaches. In preparation for the analysis of the BioNutrients samples, we have tested three mutation calling tools (GATK for Microbes, BreSeq and DiscoSNP) designed for complex samples. A challenge of validating mutation identification pipelines is a lack of “Ground Truth” datasets, especially for complex samples. To compare these three tools, we sought to identify mutations in pre-existing WGS data collected from populations of Chlamydomonas reinhardtii that were exposed to UV mutagenesis and growth in LEO as part of the Space Algae-1 mission. Here we present a summary of these tools against the analysis originally conducted using the CRISP tool. Critical metrics are compared such as runtime, the number of SNPs, the number and size of Indels, and patterns of transversion and transitions identified by each tool are reported. By sharing these benchmarking results collected in support of the BioNutrients mission, we aim to guide others seeking to identify SNVs in similarly complex microbial samples.

Biology↗

NASA NTRS1987

The growth and harvesting of algae in a micro-gravity environment

Algae growth in a micro-gravity environment is an important factor in supporting man's permanent presence in space. Algae can be used to produce food, oxygen, and pure water in a manned space station. A space station is one example of a situation where a Controlled Ecological Life Support System (CELSS) is imperative. In setting up a CELSS with an engineering approach at the Aerospace department of the University of Colorado, questions concerning algae growth in micro-g have arisen. The Get Away Special (GAS) Fluids Management project is a means through which many questions about the effects of a micro-g environment on the adequacy of growth rates, the viability of micro-organisms, and separation of gases and solids for harvesting purposes can be answered. In order to be compatible with the GAS tests, the algae must satisfy the following criteria: (1) rapid growth rates, (2) sustain viability over long periods of non-growth storage, and (3) very brief latency from storage to rapid growth. Testing indicates that the overall growth characteristics of Anacystis Nidulans satisfy the specifications of GAS's design constraints. In addition, data acquisition and the method of growth instigation are two specific problems being examined, as they will be encountered in interfacing with the GAS project. Flight testing will be two-fold, measurement of algae growth in micro-g and separation of algae from growth medium in an artificial gravitation field. Post flight results will provide information on algae viability in a micro-g environment as reflected by algal growth rates in space. Other post flight results will provide a basis for evaluating techniques for harvesting algae. The results from the GAS project will greatly assist the continuing effort of developing the CELSS and its applications for space.

Wiltberger, Nancy L.↗

NASA NTRS1963

Algae as Food for Space Travel: A Review

Algae, other plants, and animals as food for space travel

FISH↗

NASA NTRS2015

Benefits of Microalgae for Human Space Exploration

Algae have long been known to offer a number of benefits to support long duration human space exploration. Algae contain proteins, essential amino acids, vitamins, and lipids needed for human consumption, and can be produced using waste streams, while consuming carbon dioxide, and producing oxygen. In comparison with higher plants, algae have higher growth rates, fewer environmental requirements, produce far less "waste" tissue, and are resistant to digestion and/or biodegradation. As an additional benefit, algae produce many components (fatty acids, H2, etc.) which are useful as biofuels. On Earth, micro-algae survive in many harsh environments including low humidity, extremes in temperature, pH, and as well as high salinity and solar radiation. Algae have been shown to survive inmicro-gravity, and can adapt to high and low light intensity while retaining their ability to perform nitrogen fixation and photosynthesis. Studies have demonstrated that some algae are resistant to the space radiation environment, including solar ultraviolet radiation. It remains to be experimentally demonstrated, however, that an algal-based system could fulfil the requirements for a space-based Bioregenerative Life Support System (BLSS) under comparable spaceflight power, mass, and environmental constraints. Two specific challenges facing algae cultivation in space are that (i) conventional growth platforms require large masses of water, which in turn require a large amount of propulsion fuel, and (ii) most nutrient delivery mechanisms (predominantly bubbling) are dependent on gravity. To address these challenges, we have constructed a low water biofilm based bioreactor whose operation is enabled by capillary forces. Preliminary characterization of this Surface Adhering BioReactor (SABR) suggests that it can serve as a platform for cultivating algae in space which requires about 10 times less mass than conventional reactors without sacrificing growth rate. Further work is necessary to compare the performance of microalgae-based systems, including SABR, with systems based on higher plants, as well as conventional physicochemical-based systems. Ongoing and future work in our laboratory is therefore directed determining the feasibility of using algae as a component of a BLSS in space.

Algae↗

NASA NTRSDate not supplied

Determining Chlamydomonas reinhardtii resistance to ionizing radiation at a genome-wide scale

Spaceflight is a complex mixture of abiotic stresses that causes a myriad of cellular responses including increased genome-wide mutation load. The impact of spaceflight on mutation load is not well understood for most organisms and is especially critical to characterize for candidate microorganisms that could be part of biological life support systems. Prior research in our laboratory revealed an unexpectedly high level of mutation during spaceflight in the eukaryotic green algae, C. reinhardtii. Based on the spectrum of base changes observed, we concluded that the mutations were generated through a molecular mechanism unique to the spaceflight environment. Spaceflight is a complex set of stresses, and we are using an Earth-based analog to test ionizing radiation as a potential causative variable for the unique mutation spectrum observed in spaceflight. C. reinhardtii was grown exposed to chronic radiation from a Cesium-137 source. Four biological replicate cultures of wild-type cells were grown in gas permeable plastic tissue culture bags in liquid media following the design used on the International Space Station (ISS) during the previous space algae experiment. Radiation levels for this experiment approximate ionizing radiation observed on the moon, in low Earth orbit (LEO), and on Earth. Cells from each replicate were passaged to inoculate the next cycle of growth, then samples were taken from each culture to characterize cell morphology, quantify biomass, and extract DNA. Whole genome sequencing from each culture will be used to identify the frequency and types of mutations in each radiation level. In growth cycles 3 and 4, there was a significant increase in biomass accumulation under lunar radiation level compared to LEO or Earth radiation levels. These results such that ionizing radiation affected growth of C. reinhardtii.

Microbiology↗

NASA NTRSDate not supplied

Determining Chlamydomonas Reinhardtii Resistance to Ionizing Radiation at A Genome-Wide Scale

Spaceflight is a complex mixture of abiotic stresses that causes a myriad of cellular responses including increased genome-wide mutation load. The impact of spaceflight on mutation load is not well understood for most organisms and is especially critical to characterize for candidate microorganisms that could be part of biological life support systems. Prior research in our laboratory revealed an unexpectedly high level of mutation during spaceflight in the eukaryotic green algae, C. reinhardtii. Based on the spectrum of base changes observed, we concluded that the mutations were generated through a molecular mechanism unique to the spaceflight environment. Spaceflight is a complex set of stresses, and we are using an Earth-based analog to test ionizing radiation as a potential causative variable for the unique mutation spectrum observed in spaceflight. C. reinhardtii was grown exposed to chronic radiation from a Cesium-137 source. Four biological replicate cultures of wild-type cells were grown in gas permeable plastic tissue culture bags in liquid media following the design used on the International Space Station (ISS) during the previous space algae experiment. Radiation levels for this experiment approximate ionizing radiation observed on the moon, in low Earth orbit (LEO), and on Earth. Cells from each replicate were passaged to inoculate the next cycle of growth, then samples were taken from each culture to characterize cell morphology, quantify biomass, and extract DNA. Whole genome sequencing from each culture will be used to identify the frequency and types of mutations in each radiation level. In growth cycles 3 and 4, there was a significant increase in biomass accumulation under lunar radiation level compared to LEO or Earth radiation levels. These results show that ionizing radiation affected growth of C. reinhardtii.

Hope Hersh↗

NASA NTRS1989

Potential utilization of algal protein concentrate as a food ingredient in space habitats

Green alga Scenedesmus obliquus was studied as one of the potential sources of macronutrients in a space habitat. Algal protein concentrate (70.5% protein) was incorporated into a variety of food products such as bran muffins, fettuccine (spinach noodle imitation) and chocolate chip cookies. Food products containing 20 to 40% of incorporated algal proteins were considered. In the sensory analysis the greenish color of the bran muffins and cookies was not found to be objectional. The mild spinachy flavor (algae flavor) was less detectable in chocolate chip cookies than in bran muffins. The color and taste of the algae noodles were found to be pleasant and compared well with commercially available spinach noodles. Commercially available spray-dried Spirulina algae was also incorporated so the products can be compared with those containing Scenedesmus obliquus concentrate. Food products containing commercial algae had a dark green color and a "burnt after taste" and were less acceptable to the panelists.

NASA Discipline Life Support Systems↗

NASA NTRS2020

Quantifying Spatiotemporal Variability of Glacier Algal Blooms and the Impact on Surface Albedo in Southwestern Greenland

Albedo reduction due to light-absorbing impurities can substantially enhance ice sheet surface melt by increasing surface absorption of solar energy. Glacier algae have been suggested to play a critical role in darkening the ablation zone in southwestern Greenland. It was very recently found that the Sentinel-3 Ocean and Land Colour Instrument (OLCI) band ratio R709 nm∕R673 nm can characterize the spatial patterns of glacier algal blooms. However, Sentinel-3 was launched in 2016, and current data are only available over three melting seasons (2016–2019). Here, we demonstrate the capability of the MEdium Resolution Imaging Spectrometer (MERIS) for mapping glacier algae from space and extend the quantification of glacier algal blooms over southwestern Greenland back to the period 2004–2011. Several band ratio indices (MERIS chlorophyll a indices and the impurity index) were computed and compared with each other. The results indicate that the MERIS two-band ratio index (2BDA) R709 nm∕R665 nm is very effective in capturing the spatial distribution and temporal dynamics of glacier algal growth on bare ice in July and August. We analyzed the interannual (2004–2011) and summer (July–August) trends of algal distribution and found significant seasonal and interannual increases in glacier algae close to the Jakobshavn Isbrae Glacier and along the middle dark zone between the altitudes of 1200 and 1400 m. Using broadband albedo data from the Moderate Resolution Imaging Spectroradiometer (MODIS), we quantified the impact of glacier algal growth on bare ice albedo, finding a significant correlation between algal development and albedo reduction over algae-abundant areas. Our analysis indicates the strong potential for the satellite algal index to be used to reduce bare ice albedo biases in regional climate model simulations.

surface albedo↗

NASA NTRS1990

Algae for controlled ecological life support system diet characterization of cyanobacteria 'spirulina' in batch cultures

Spirulina sp. is a bioregenerative photosynthetic and edible alga for space craft crews in a Closed Ecological Life Support System (CLESS). It was characterized for growth rate and biomass yield in batch cultures, under various environmental conditions. The cell characteristics were identified for one strain of Spirulina: S. maxima. Fast growth rate and high yield were obtained. The partitioning of the assimulatory products (proteins, carbohydrates, lipids) were manipulated by varying the environmental conditions. Experiments with Spirulina demonstrated that under stress conditions carbohydrate increased at the expense of protein. In other experiments, where the growth media were sufficient in nutrients and incubated under optimum growth conditions, the total proteins were increased up to almost 70 percent of the organic weight. In other words, the nutritional quality of the alga could be manipulated by growth conditions. These results support the feasibility of considering Spirulina as a subsystem in CELSS because of the ease with which its nutrient content can be manipulated.

Tadros, M. G.↗

NASA NTRS1988

Characterization of Spirulina biomass for CELSS diet potential

Spirulina sp. as a bioregenerative photosynthetic and an edible alga for space craft crew in a CELSS, was characterized for growth rate and biomass yield in batch cultures, under various environmental conditions. The cell characteristics were identified for two strains of Spirulina: S. maxima and S. plantensis. Fast growth rate and high yield of both strains were obtained under the following conditions: temperature (30 to 35 C), light irradiance (60 to 100 uE/m/s), nitrate (30 mM), phosphate (2 mM), aeration (300 ml/min), and ph (9 to 10). The partitioning of the assimalatory products (proteins, carbohydrates, lipids) were manipulated by varying the environmental growth conditions. The experiments with Spirulina demonstrated that under stress conditions (high light 120 uE/m/s, temperature 38 C, nitrogen or phosphate limitation; 0.1 M sodium chloride) carbohydrate increased at the expense of protein. In other experiments, where the growth media were sufficient in nutrients and incubated under optimum growth conditions, the total proteins were increased up to almost 70 percent of the organic weight. Conclusion: The nutritional quality of the alga could be manipulated by growth conditions, and therefore usful as a subsystem in CELSS.

Tadros, Mahasin G.↗