Supporting information for the assumptions and calculations can be found in the Supplementary Information . In addition to supplying nutrients, this single serving will assist with other aspects of life support. It also serves to revitalize water as 9.7and 22.8liters per day of clean water are released in gaseous form via transpiration, most of which can be recycled for crop cultivation unless needed in other operations, such as for pharmaceutical formulations. These simple calculations highlight the auxiliary value of plants for bio-regenerative life support. The contributions to all aspects of life support depend highly on the crop species and cultivation environment. For example, a previous study using a closed human/plant system has shown experimentally that 11.2 m2 of wheat grown at high light intensity supplies sufficient oxygen for one person. Wheat is one of the most productive crops for oxygen production, which is amplified by the high light intensity used and its tolerance of a 24-h light cycle.In addition to traditional life support metrics like oxygen productivity, crop selection for molecular pharming must also take into account factors such as the efficiency of transformation and characteristics of the host cell protein compared to the product target.Table 2 summarizes the key assumptions that were built into the two test cases. The logic for selection of the production method is shown in Figure 4 and further described in the Supplementary Information . From the perspective of molecular pharming,ebb and flow trays lettuce serves as a fast-growing crop with a small cultivation footprint in which the edible biomass is also the expressible biomass capable of producing pharmaceuticals. Potato represents a slow-growing crop that has the advantage of distinct edible biomass and expressible biomass ; molecular pharming would not significantly impact the total available food resource.

Leaves detached from the intact plant are capable of providing comparable pharmaceutical yields to those from the intact plant. Production of pharmaceuticals in inedible biomass is one way to create physical separation of the food and pharmaceutical streams while maintaining resource flexibility. However, there are situations in which it may be advantageous for merged food and pharmaceutical streams; there are reports in literature on oral delivery of pharmaceuticals in both lettuce and potato tubers. While promising, this technology is still in the early stages of development. As shown in Figure 5, only 10.4 g FWis needed for the Test Case 1 acute disease state countermeasure in potato, while 36.9 g FWis needed for the Test Case 2 chronic disease state countermeasure in lettuce. While these test cases are driven by conservative assumptions of performance well-established in literature, it is important to note that biomass requirements are highly dependent on the rate of pharmaceutical accumulation , medication dose size, and drug delivery modality. Figure 6 illustrates how the total crop biomass demand differs between the two test cases based on the medication demand and over a range of conservatively estimated molecular pharming expression levels, while Figure 6 shows how the biomass requirements depend on drug delivery modality.Since the founding of modern biotechnology with Cohen and Boyer’s discovery of recombinant DNA technology in 1973, biological organisms have risen to prominence as the primary means for producing high value pharmaceutical proteins and other products, most of which are too complex to be economically and sustainably produced using current chemical synthesis approaches. In the half-century since inception of recombinant DNA technology, a plethora of biological platforms have been engineered as factories of recombinant products – microbial culture, eukaryoticcell culture, live animals, cell lysates, and whole plants.

Table 3 shows a comparison of current pharmaceutical production platforms based on attributes relevant to their deployment for human health in space. Details of the category definition and system rankings are included in Supplementary Information. There are also new platforms on the horizon for production and drug delivery .Commercial biopharmaceutical manufacturing on Earth is dominated by microbial fermentation and mammalian cell culture. Spread across over 1,700 production facilities globally, there is a commercial production capacity of 4.8 million liters for microbial fermentation and 15.0 million liters mammalian cell culture . Regulatory pathways have been well established, decades of intensive research have seen orders of magnitude increase in productivity, and billions of dollars have been invested into developing a culture-based system infrastructure. However, this established dominance of culture based systems does not easily translate into the implementation of human health in space for several reasons. The most glaring difficulty is with cell culture behavior, both with the cell biology and fluid dynamics, in altered gravity; operation will need to be compatible with micro-gravity for in-flight production and reduced gravity for a Moon or Mars mission. There is a growing body of literature on the development of bioreactors with alternative containment and mixing for micro-gravity. The main existing technical difficulties of culture-based systems in limited resource environments are the expensive and complex equipment requirements and the need for the aseptic operation for growing production host cells. Microbial fermenters and cell culture bioreactors are made of glass and/or a special grade stainless steel for durability and corrosion resistance. Bioreactors are generally designed with a suite of capabilities, including: culture agitation, aeration, sampling, in-line sensing, feedback control systems , cleaning, and sterilization. This complex process equipment lowers general accessibility and increases the workforce specialization of operators, which in turn forms another barrier to application in limited resource environments. The equipment burden of culture-based systems is largely a result of the need to maintain a sterile cultivation environment during operation.

Without adequate environmental protection, cultures are susceptible to contamination by undesired organisms.In addition to complexity, stainless steel bioreactors impose significant mass and volume penalties that might prohibit adoption in a space mission. For example, a typical glass and stainless steel stirred tank reactor for 1 L working volume of culture weighs 3.7 kg, not including liquid culture mass and auxiliary reactor components . A growing trend in culture-based systems is to employ single-use technology for cost-savings in cleaning validation, capital costs, and time. Single-use technology for culture-based systems typically consists of a multi-layered plastic bag used in lieu of, or with support of, a stainless steel vessel. Of specific importance to space missions, these savings could also translate into significant reductions in mass and volume requirements. However, as the name “single-use” states, these plastic bioreactor housings are only used once, introducing significant consumable and waste streams to the pharmaceutical foundry. Therefore, single-use technology may introduce reliance on a stable supply chain for consumables that could strain feasibility in a limited resource environment. The use of recyclable materials for single-use technology has not been commercially implemented but would serve to alleviate these concerns. The hindrance of consumable waste is offset by reduced cleaning requirements and should be evaluated within a mission architecture. For example, if pharmaceutical production is projected to be below a threshold capacity, then the extra consumables required to be flown may be acceptable. Exceptional to the typical culture-based system vulnerabilities, microbial, oxygenic photoautotrophic cultures represent a promising subset of culture-based systems that may be better equipped for supporting human life in space. They share many of the same benefits of molecular pharming; these organisms are able to use available in situ resources as feed stocks, and some have been shown to be quite tolerant to a range of water qualities. Additionally, some of these species have unique advantageous characteristics. They can serve as a food resource, grow under conditions that minimize the probability of contamination, and even be used as bio-fertilizer to improve soil quality and crop productivity. A subset of these organisms,4×8 flood tray including the microalgal species Chlamydomonas reinhardtii and Chlorella vulgaris, and the cyanobacterial species Arthrospira platensis , is categorized by the U.S. Food and Drug Administration as being Generally Recognized as Safe , whereby these organisms are considered edible and are sold commercially as food and nutritional supplements. The edible nature of these organisms presents a potential advantage to pharmaceutical foundries in space in that if the target production molecules are bio-available through simply eating the wet or dry biomass of the production host, no downstream purification is needed. The microbial nature of these organisms provides potential advantages to plant systems. First, microalgae and cyanobacteria have genetic tools that are typically more advanced than those of plants . Although tools for engineering A. platensis have been reported, engineering this organism has remained a challenge in the field. To this end, we have recently developed a genetic toolkit for creating stable mutants of A. platensis that will help unlock this organism for metabolic engineering goals. Second, these organisms have faster growth rates than plants, which enables shorter times to reach the biomass necessary for molecular harvesting. Third, the larger metabolic diversity of microalgae and cyanobacteria compared to plants could help to metabolically engineer target molecules that are difficult or impossible to produce in plants using current technologies. Therefore, these organisms may be well suited for pharmaceutical production, or for enhancing the nutritional load through vitamin supplementation. Thus, GRAS-status microbial oxygenic photoautotrophs are poised to become edible molecular pharming hosts for space missions. As these technologies continue to mature, a detailed techno-economic comparison between plants, microalgae, and cyanobacteria will be needed. It may be that a robust pharmaceutical foundry for space ends up being less about selecting one system and more about selecting a network of systems. It is important that interconnectivity and synergy of different platforms be considered for biological-based production of pharmaceuticals and other high-value products to support human life .

A main distinguishing feature of whole plants as a pharmaceutical production platform is the freedom from complex equipment housing during operation; the supracellular structure of a plant serves as its own natural “bioreactor” for operational controland protection against contamination. This effectively means that molecular pharming can be employed with lower complexity process control systems and equipment. Figure 7 illustrates the simplicity and linear scalability of producing pharmaceuticals in whole plants as compared to culture-based systems. However, an equivalent system masscomparison of molecular pharming and culture-based systems for spaceflight is needed to rigorously evaluate the perceived advantage of molecular pharming simplicity. This self-regulating behavior also suggests that plants may serve as a more robust production platform with higher tolerance to input quality variation for given output product quality. In the literature, the strength of molecular pharming production tolerance as compared to culture-based systems is as yet unproven, but would be a valuable avenue of research to directly investigate.For decades, plants have been identified as important life support objects for human health in space. Here we have presented the need for an Earth-independent pharmaceutical life support system and identified molecular pharming as a strategy to tap into the power of plants to serve as a pharmaceutical foundry to meet that need. Molecular pharming in space has the potential to provide manufacturing capacity to respond to both acute and chronic disease states in space with a relatively small amount of plant biomass. Selecting the set of the most appropriate molecular pharming-based production strategies should be carried out within a reference mission architecture, which considers key attributes that we have laid out here. There are many ways to envision pharmaceutical foundries for interplanetary use. Chemical synthesis is limited in production targets and in reagent supply but it may be necessary when biology is not sufficient or capable . Translating culture based systems from Earth to space utility faces the challenges of cell biology, fluid dynamics, feed stock sustainability, mass/volume penalties, and crew training. Their relatively high productivity may position them as an effective platform for settlement missions to sustain larger populations. Autotrophic cultures are exceptional solutions to several challenges of traditional culture based systems and have more potential as a near term platform. More thorough investigation is needed to select an appropriate set of pharmaceutical foundries. Process mass intensityis a metric recently adopted by the bio-pharmaceutical industry to measure the environmental footprint of production. PMI is defined as the total mass in kg of raw material and consumable inputs to produce 1 kg of active pharmaceutical ingredient. PMI can serve as a useful reference point when performing ESM analyses of pharmaceutical foundries in space.