The Potential Use of Microalgae for Nutrient Supply and Health Enhancement in Isolated and Confined Environments

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Microalgae have photosynthetic conversion efficiency about three times that of higher plants and need only 1.7-5.4 m2 of land per gram of protein, less than meat and poultry.

“They exhibit photosynthetic conversion efficiency three times greater than higher plants, and the land requirement per gram of protein is only 1.7-5.4m 2 , significantly lower than that of conventional protein sources such as meat and poultry (Sobhi et al., 2023).”

• cites Sobhi et al., 2023Not checked yet

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Polar microalgae have very low light requirements and can thrive, reproduce, and survive at constant low temperatures higher than their natural habitats.

“These microalgae have very low light requirements and are capable of thriving, reproducing, and surviving at constant low temperatures that are significantly higher than those recorded in their natural habitats (Ma et al., 2018).”

• cites Ma et al., 2018Not checked yet

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Nannochloropsis under weak light performs rapid photosynthesis via efficient light-harvesting, resulting in higher growth rate and fatty acid conversion efficiency.

“Under weak light intensity, Nannochloropsis can utilize its complex and efficient light-harvesting and energy conversion mechanisms to perform rapid photosynthesis, resulting in a higher growth rate and fatty acid conversion efficiency (Ma et al., 2018).”

• cites Ma et al., 2018Not checked yet

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UVA exposure tends to increase EPA and PUFA levels in Phaeodactylum tricornutum, while combined UVA and UVB increases saturated and monounsaturated fatty acids and suppresses PUFA in Chaetoceros muelleri.

“Upon exposure to UVA radiation, eicosapentaenoic acid (EPA) and polyunsaturated fatty acid (PUFA) levels in Phaeodactylum tricornutum tended to increase, whereas combined UVA and UVB radiation enhanced the production of saturated fatty acids (SFAs) and monounsaturated fatty acids, while suppressing PUFA in Chaetoceros muelleri (Liang et al., 2006).”

• cites Liang et al., 2006Not checked yet

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Fulvic acid stimulation of Haematococcus pluvialis increases biomass concentration and astaxanthin content.

“Stimulation of Haematococcus pluvialis with fulvic acid during the growth process resulted in an increased biomass concentration and astaxanthin content (Zhao et al., 2015).”

• cites Zhao et al., 2015Not checked yet

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Chlorella has high photosynthetic efficiency at 150-350 μmol/m2/s and tolerates temperature and pH fluctuations, making it suited to confined environments.

“Chlorella, the most prevalent edible microalgae, exhibits high photosynthetic efficiency at 150-350 µmol/m 2 /s and notable adaptability to temperature and pH fluctuations, allowing it to thrive and accumulate substances across a wide temperature range and under weakly acidic to weakly alkaline pH conditions, making it well suited for confined environments (Bhola et al., 2011).”

• cites Bhola et al., 2011Not checked yet

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Microalgae contain essential amino acids, unsaturated fatty acids, polysaccharides, and functional compounds such as astaxanthin, carotenoids, and polyphenols that provide health benefits.

“Microalgae possess a wide array of nutrients, including essential amino acids, unsaturated fatty acids (UFAs), and polysaccharides, which fulfill the fundamental nutritional requirements of the human body, along with functional compounds, such as astaxanthin, carotenoids, and polyphenols, which confer significant health benefits (Chen, Qian, He, et al., 2022).”

• cites Chen, Qian, He, et al., 2022Not checked yet

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Low-frequency ultrasound and nitrogen limitation increase Chlorella biomass by 32.1% and lipid accumulation by 44.5%.

“Using lowfrequency ultrasound and nitrogen limitation, Chlorella exhibited a substantial increase in biomass of 32.1% and lipid accumulation of 44.5% (Wei et al., 2022).”

• cites Wei et al., 2022Not checked yet

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Microalgal cells and bioactive components modulate the immune system and exhibit strong immunostimulatory effects in human and mouse models.

“Recent studies revealed that microalgal cells and their bioactive components modulate the immune system and exhibit strong immunostimulatory effects in both human and mouse models (Riccio & Lauritano, 2020).”

• cites Riccio & Lauritano, 2020Not checked yet

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• AssumptionRests on an assumption: Findings from animal and cell models used in the review can be generalized to humans in isolated and confined environments.

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In a mouse tail suspension model, dietary astaxanthin inhibits tissue hydrogen peroxide increase, attenuates mitochondrial oxidative stress, mitigates apoptosis, and prevents muscle weight loss.

“A mouse tail suspension model was used to investigate the effects of astaxanthin on mitochondrial dysfunction characterized by lipid bilayer disruption and subsequent muscle weight loss, demonstrating that the administration of astaxanthin through dietary intake could effectively inhibit the increase in tissue hydrogen peroxide, attenuate mitochondrial oxidative stress, mitigate mitochondriamedi”

• cites Sun et al., 2021Not checked yet

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• AssumptionRests on an assumption: Findings from animal and cell models used in the review can be generalized to humans in isolated and confined environments.

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Using microalgae as a novel food source can provide diverse nutrients and improve crew sensory satisfaction, thereby supporting sustainability.

“From a dietary perspective, incorporating microalgae as a novel food source not only provides diverse nutrients but also enhances the sensory satisfaction of crew members, thereby promoting sustainability.”

• AssumptionRests on an assumption: Vibrant food colors can stimulate appetite, create novelty and differentiation, evoke health and pleasure, and alleviate psychological stress.

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In mice with depression, astaxanthin pretreatment significantly reduced the denatured cell index and nuclear pyknosis and increased cytoplasmic concentration in the hippocampus.

“The authors observed that pretreatment with astaxanthin resulted in a significant reduction in the denatured cell index and nuclear pyknosis, accompanied by an enhanced cytoplasmic concentration in the hippocampus.”

• cites Qiao et al., 2017Not checked yet

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There is a lack of compelling preclinical and clinical evidence on the therapeutic potential of various microalgal species and components, mainly because existing research relies on limited-duration rodent models.

“Despite the notable therapeutic effects exhib-ited by various species and constituents of microalgae, there is a dearth of compelling evidence from preclinical and clinical studies on the therapeutic potential of various species and components of microalgae, primarily because of the reliance on limited-duration rodent models in existing research (Slattery & Cryan, 2012).”

• cites Slattery & Cryan, 2012Not checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The mechanisms behind appetite suppression and depressive emotions in these environments still require further study.

“However, the mechanisms underlying appetite suppression or the development of depressive emotions in these three environments still need to be further elucidated (Da Silva et al., 2002).”

• cites Da Silva et al., 2002Not checked yet

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Spirulina exhibited efficient targeted therapy in a 4T1 breast cancer lung metastasis mouse model, enhanced by its charge and fluorescence characteristics, enabling tracking of the system's in vivo movement.

“Utilizing its threedimensional (3D) spiral structure and negative charge, Spirulina exhibited efficient targeted therapy in a 4T1 breast cancer lung metastasis mouse model, as reported by Zhong et al. (2020b), which was further enhanced by its charge and fluorescence characteristics, enabling targeted tracking of the system's in vivo movement.”

• cites Zhong et al., 2020bNot checked yet

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Probably not a substantial claim: may not pass S4 (based). May combine two claims.

Sustainable in situ growth and processing of microalgae in confined environments could provide fresh acceptable green food and improve emotional and psychological well-being.

“Enabling sustainable growth and in situ processing of microalgae in these environments could offer fresh and acceptable green food options while also enhancing the emotional and psychological well-being of individuals.”

• AssumptionRests on an assumption: Transporting fresh produce such as vegetables and fruits over long distances and time challenges freshness and can cause digestive and gut microbiota disturbances, hampering the food supply.

Probably not a substantial claim: may not pass S2 (checkable).

The promising therapeutic effects of microalgae provide important guidance for their use in special environments.

“Nevertheless, the promising therapeutic effects of microalgae offer important guidance for their use in special environments.”

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Cyanobacteria, especially Spirulina, are the main source of phycocyanin, which accounts for more than 15% of their dry weight.

“Cyanobacteria, especially Spirulina, are the main source of phycocyanin, accounting for more than 15% of its dry weight (Chacón-Lee & Gonzalez-Marino, 2010).”

• cites Chacón-Lee & Gonzalez-Marino, 2010Not checked yet

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PUFAs purified from microalgae show superior effects against E. coli and P. aeruginosa, potentially reducing microbial contamination risk in IACEs.

“The purification of various PUFAs, such as palmitic acid, γ-linolenic acid, and fatty acid methyl esters from microalgae, has shown superior effects against Escherichia coli and Pseudomonas aeruginosa, which may potentially reduce the risk of microbial contamination in IACEs.”

Probably not a substantial claim: may not pass S4 (based). May combine two claims.

Compared to fish oil products, microalgal lipids have wider applicability and lower production costs, offering potential as alternative sources for future functional formulations.

“Compared to fish oil products, microalgal lipids demonstrate a wider range of applicability and lower production costs, thereby offering promising potential as alternative sources for future novel functional formulations.”

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Edible microalgae such as C. vulgaris, Nannochloropsis sp., and Schizochytrium have potential for UFA synthesis and bioactivities including prevention of dyslipidemia, glucose metabolism regulation, immune enhancement, and anti-inflammatory effects.

“Edible microalgae, including C. vulgaris, Nannochloropsis sp., and Schizochytrium, exhibit exceptional potential for UFA synthesis and exhibit significant biofunctional activities, such as the prevention of dyslipidemia, regulation of glucose metabolism, enhancement of the immune response, and anti-inflammatory effects.”

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Aeruginosins from Microcystis are linear tetrapeptides with strong affinity for serine proteases and are effective for thrombosis treatment and prevention.

“Aeruginosins, isolated from Microcystis, are a class of linear tetrapeptide compounds that exhibit a strong affinity for serine proteases and serve as effective tools for the treatment and prevention of thrombosis (Ersmark et al., 2008).”

• cites Ersmark et al., 2008Not checked yet

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Microalgae, especially those from extreme environments, can produce substantial lipids and are promising suppliers of unsaturated fatty acids.

“These studies demonstrated the remarkable ability of microalgae, particularly in extreme environments, to produce substantial amounts of lipids, making them highly promising suppliers of UFAs.”

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Microalgae proteins have good gelation and foaming properties and remain stable over wide temperature and higher ionic strength.

“Microalgae proteins exhibit excellent gelation and foaming properties and can maintain good stability over a wide range of temperatures and higher ionic strengths (Bertsch et al., 2021).”

• cites Bertsch et al., 2021Not checked yet

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Engaging with nature or natural environments and interacting with plants and surroundings can reduce anxiety, depression, and mood disorder symptoms, lower perceived stress, enhance self-awareness, and promote focused attention.

“Research indicates that engaging with nature or immersing oneself in a natural environment, thereby interacting with plants and one's surroundings, can effectively diminish symptoms of anxiety, depression, and mood disorders, alleviate perceived stress levels, enhance self-awareness, and promote focused attention (Gonzalez et al., 2011).”

• cites Gonzalez et al., 2011Not checked yet

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Microalgae proteins have contents of 40-50% and over 70% in some species, exceeding soybeans and milk.

“Microalgae, an emerging protein source, distribute proteins among various cellular compartments, such as the cytoplasm, organelles, and cell walls, with contents ranging from 40% to 50% and even over 70% in some species, surpassing soybeans and milk in terms of protein content (Szabo et al., 2013).”

• cites Szabo et al., 2013Not checked yet

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Microalgal nutrients have antioxidant, antibacterial, and anti-inflammatory activities, making algal cells and extracts valuable for food and medicine.

“Nutrients derived from microalgae exhibit diverse biological activities, including antioxidant, antibacterial, and anti-inflammatory properties, making both the entire algal cell and its cellular extracts valuable resources for food and medicine.”

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Microalgal components can modulate depression-related pathways and have significant therapeutic effects in depression treatment.

“Additionally, microalgal components have been shown to modulate depression-related pathways and exhibit significant therapeutic effects in the treatment of depression (Subermaniam et al., 2021).”

• cites Subermaniam et al., 2021Not checked yet

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Phycobiliproteins are widely recognized and used in food and dietary supplements as additives or natural blue dye sources.

“Having gained extensive recognition in the United States and the European Union, this essential natural pigment is widely acknowledged and regularly utilized in the fields of food and dietary supplements, primarily serving as an additive or natural blue dye source in various products, including chewing gum, dairy products, ice cream, and jellies (Joshua et al., 2021;Ma et al., 2022).”

• cites Joshua et al., 2021Not checked yet

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• cites Ma et al., 2022Not checked yet

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Hexapeptide WPRGYF from Tetradesmus obliquus protein has antioxidant and ACE inhibitory activities confirmed in vitro.

“A hexapeptide, WPRGYF, derived from the enzymatic hydrolysis of Tetradesmus obliquus protein, was isolated, and its excellent antioxidant and ACE inhibitory activities were experimentally confirmed in vitro (Montone et al., 2018).”

• cites Montone et al., 2018Not checked yet

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Microalgae can serve as nutritional components with health-enhancing effects and as biomedical materials with efficacy in drug delivery, oxygen donation, photodynamic therapy, and wound healing.

“Given their distinctive structure and biological traits, microalgae have been shown to serve not only as nutritional components with remarkable health-enhancing effects but also as biomedical materials with greater efficacy, including drug delivery, oxygen donation, photodynamic therapy, and wound healing functions.”

Classified as probably not a substantial claim. May combine two claims.

Current microalgae research for human health focuses mainly on bioactive substances, while medical-related studies are nascent with limited application scenarios and inadequate data on biological safety and efficacy.

“Current research on microalgae with respect to human health benefits predominantly focuses on their diverse bioactive substances, whereas medicalrelated studies are in the nascent stage, with limited application scenarios and inadequate data on biological safety and efficacy.”

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Isolation and refinement of microalgal proteins and lipids can optimize nutrient utilization, mitigate the sensory perception of whole microalgal products, and enhance bioaccessibility.

“Furthermore, the implementation of appropriate techniques for the isolation and refinement of essential constituents such as microalgal proteins and lipids can be specifically aimed at optimizing the utilization of diverse microalgal nutrients, thus effectively mitigating the impact of sensory perception associated with overall microalgal products while simultaneously enhancing their bioaccess”

Probably not a substantial claim: may not pass S2 (checkable).

Microalgae serve as attractive food sources for enhanced nutrition and health in unique environments.

“In summary, microalgae serve as attractive food sources for enhanced nutrition and health in unique environments.”

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Despite evidence that microalgae are vital for renewable life-support systems in space missions, current research is mostly limited to small-scale cultivation models.

“Despite mounting evidence indicating the vital role of microalgae as a crucial component of renewable lifesupport systems in domains such as space exploration to serve the entire mission, current research is predominantly restricted to the exploration of microalgal growth under limited small-scale cultivation models.”

Probably not a substantial claim: may not pass S4 (based).

Under limited medical resources in isolated and confined environments, precision microalgal engineering and printable biomaterials provide a new approach to ensure crew medical support and technological innovation.

“However, under the conditions of limited medical resources in IACEs, the development of precision microalgal engineering and the preparation of various types of printable biomaterials provide a new approach to ensure medical support for crew members and technological innovation.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

Customized 3D and 4D food printing can be achieved by using computer-aided designs and diverse processing methods.

“Customized 3D and 4D food printing can be achieved by leveraging computeraided designs and diverse processing methods.”

Probably not a substantial claim: may not pass S4 (based).

Synthetic biology may offer a more effective and rapid approach than conventional biological and nonbiological stimuli for promoting nutrient accumulation in microalgae.

“In addition to conventional biological and nonbiological stimuli for metabolic processes, synthetic biology may offer a more effective and expeditious approach for promoting nutrient accumulation.”

Probably not a substantial claim: may not pass S2 (checkable).

Providing a more diversified and healthier range of microalgae-based food products, if product safety is ensured, holds promise for reducing stress and improving health maintenance.

“Under the premise of ensuring product safety, the provision of a more diversified and healthier range of microalgae-based food products holds promise for reducing stress and providing superior benefits for health maintenance.”

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Bioreactors are crucial for high-density microalgae cultivation because they provide a closed environment that prevents contamination and allows precise regulation of temperature and pH.

“The development of bioreactors is crucial for addressing the key challenge of achieving high-density microalgae cultivation, as these bioreactors offer a closed environment that safeguards microalgae from contamination while enabling precise regulation of cultivation parameters, including temperature and pH (Peter et al., 2022).”

• cites Peter et al., 2022Not checked yet

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Improving and enhancing the flavor of microalgae can positively affect appetite stimulation and reduce psychological stress.

“Improving and enhancing the flavor of microalgae can positively impact appetite stimulation and psychological stress reduction.”

Probably not a substantial claim: may not pass S4 (based).

Environmental constraints present significant challenges in sustaining the food supply.

“Nevertheless, environmental constraints present significant challenges in sustaining the food supply.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

Physicochemical approaches such as heat degradation, solid adsorbents, ethanol solvent absorption, and nanocapsule particles can directly remove volatile substances.

“Various physicochemical approaches, such as heat degradation, solid adsorbents, solvent absorption using ethanol, and nanocapsule particles, can directly contribute to the removal of volatile substances.”

Probably not a substantial claim: may not pass S4 (based).

Numerous species of microalgae can thrive and maintain metabolic activity in restricted spaces.

“Numerous species of microalgae have the capacity to thrive and maintain their metabolic activity in restricted spaces.”

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Co-printing C. reinhardtii and SaOS-2 human osteoblast cells onto alginate scaffolds significantly increased osteoblast proliferation, attributed to active oxygen release from microalgae supporting SaOS-2 metabolism.

“Lode et al. (2015) demonstrated significant increases in osteoblast cell proliferation by co-printing C. reinhardtii and SaOS-2 human osteoblast cells onto alginate scaffolds, which was attributed to the active oxygen release of microalgae to support SaOS-2 cellular metabolism.”

• cites Lode et al., 2015Not checked yet

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Probably not a substantial claim: may not pass S4 (based).

Current understanding of the production and metabolic mechanisms of flavor compounds in microalgae remains insufficient.

“However, the current understanding of the production and metabolic mechanisms of flavor compounds in microalgae remains insufficient.”

Probably not a substantial claim: may not pass S4 (based). May combine two claims.

When faced with environmental stress, many microalgae exhibit accelerated growth rates and increased accumulation of bioactive substances.

“Furthermore, when faced with environmental stress, many microalgae exhibit accelerated growth rates and an increased accumulation of bioactive substances.”

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A diverse range of photobioreactors exists, including flat, tubular, horizontal, inclined, vertical, and biofilm reactors, with specialized designs for microgravity.

“Considering multiple factors, such as the cultivated species, farming scale, and cultivation requirements, a diverse range of photobioreactors are available, including flat, tubular, horizontal, inclined, vertical, and biofilm reactors, with further developments and discussions on specialized microalgae reactors designed particularly for specific environments such as microgravity (Wagner et al., 2”

• cites Wagner et al., 2015Not checked yet

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Probably not a substantial claim: may not pass S2 (checkable).

The confluence of environmental factors, microalgal physiological characteristics, processing techniques, bioavailability, and nutritional properties can maximize microalgae's contribution to food and health in isolated and confined environments.

“Consequently, as shown in Figure 3, the confluence of environmental factors, microalgae physiological characteristics, process-ing techniques, bioavailability, and nutritional properties embodies a potent alliance, maximizing the expansion of microalgae in enhancing food and health in IACEs.”

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Gel patches containing Spirulina showed microalgal growth and photosynthetic efficiency and promoted angiogenesis, cell proliferation, and migration at injury sites through oxygen and active substances, accelerating wound healing.

“Gel patches containing Spirulina demonstrated impressive growth and photosynthetic efficiency in microalgae while promoting angiogenesis, cellular proliferation, and migration at the injury site through the efficient release of oxygen and active substances derived from microalgae, thereby accelerating wound healing (Chen et al., 2020).”

• cites Chen et al., 2020Not checked yet

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Overall limited sensory acceptance of microalgae is a significant hurdle to their use as a novel food source, despite some species having pleasant floral and seafood aromas.

“Although certain species possess pleasant floral and seafood aromas, the overall limited sensory acceptance of microalgae poses a significant hurdle to their application as a novel food source.”