To produce 18 m3 of three-dimensional printed habitat structure on Mars encompassing a volume of 120 m3 for six crew, a current estimate of shipped mass cost is 24 T, of which 11.4 T is dry salts to mix with the MgO in the Martian soil for printer feed stock.Substituting this mixture with PHB, which has a density of 1250 kg m23 , the required 18 m3 of habitat has a mass of 22 500 kg.Consider the following unoptimized bio-manufacture scenario: two 2000 l bioreactors, each at a working volume of 1500 l, resulting in the production of 111.6 kg d21 of PHB.In this scenario, 202 days are needed to synthesize 22 500 kg of PHB, an identical duration as that required for methane bio-manufacture.The total empty mass of the bioreactors is 1.6 T , an 86% savings over the 11.4 T of shipped dry salts.Drawn power can be calculated to be 7.221 W using, and the volumetric size of the bioreactors works out to be 9.896 m3.It should be possible to improve the PHB accumulation percentage of A.platensis with synthetic biology approaches, because such techniques have allowed the cyanobacterium Synechococcus sp.PCC7002 to stably accumulate PHA at up to 52% of the cell dry mass when using the complementation of a cyanobacterial recA null mutation with the Escherichia coli recA gene on a plasmid expression system.Synthetic biology efforts to combine the benefits of C.necator with the cyanobacterium SynechocysThis sp.PCC 6803 of §3.3 have also been documented.Such efforts are important because they lend credence to the idea of one organism that is capable of producing multiple commodities: fuel, biopolymers and as we shall see,dutch bucket hydroponic possibly pharmaceuticals as well.At present, workarounds for accelerated pharmaceutical expiry involve the launch of one or more small unmanned spacecraft to restock crew supplies as needed.

However, the practicality of these missions hinges on the location of a supply depot, conducive launch opportunities, travel time, etc., with corresponding implications on astronaut health in the event of a medical emergency.Thus, the cost of pharmaceutical shelf-life includes the cost of crew safety in addition to the cost of a resupply mission.The former is not easy to quantify but is regarded as paramount to reduce.The advantageous role of biotechnology in pharmaceutical manufacture is known, and examples include antibiotics, antibiotic alternatives such as bacteriophages , and even cancer chemotherapy.Biotechnology can also facilitate the synthesis of antibiotics such as doxycycline and tetracycline from an acetate substrate, albeit with involved steps.To tackle the typically complicated substrate sequence and pathway identification problem to desirable chemical targets, a computerized suite of tools has been recently developed.This platform also suggests the amount of synthetic biological engineering that is necessary to accomplish the manufacture of the target.For instance, Anderson et al.explain how acetaminophen can be produced by modifying the chorismate pathway , wherein p-aminobenzoic acid that is made from chorismate is transformed into 4-aminophenol using the 4ABH gene taken from a mushroom, and this 4-aminophenol can then be used as a substrate to produce acetaminophen with the E.coli nhoA gene.Unfortunately, this strain is not directly suitable for space application, on account of the reduced availability of the resources that the strain uses.However, it should be possible to implement the above path to acetaminophen by harnessing a similar chorismate pathway in an autotroph of electronic supplementary material, table S1 that uses readily available inputs on space missions.The cyanobacterium SynechocysThis sp.PCC 6803, for example, has the genes for chorismate synthase and the trpG and trpE genes that are homologues of the respective E.coli pabA and pabB genes, allowing it to generate an analogue of p-aminobenzoic acid called anthranilate.Moreover, anthranilate can also be acted upon by the 4ABH gene and 4-aminobenzoate hydroxylase.It is therefore plausible that acetaminophen can be synthesized by SynechocysThis sp.PCC 6803 after the insertion of the 4ABH and nhoA genes , and testing of this hypothesis in the near-future is anticipated.

As Ungerer et al.indicate, unnatural gene insertions into SynechocysThis sp.PCC 6803 and subsequent organism optimization can allow for a substantial rate of production of a desired target.It is possible to estimate the volumetric yield of acetaminophen bio-manufacture in SynechocysThis sp.PCC 6803 with the data in: an equivalent carbon output for the reported productivity rate of 171 mg l21 d21of ethylene occurs when 1.5 mmol l21 d21 of acetaminophen is produced, i.e.230 mg l21 d21.This yield is sufficient, because pharmaceuticals require low concentrations of an active ingredient, for example, a single tablet dose of acetaminophen is 325 mg.Hence, even accounting for losses, only a few days of acetaminophen manufacture starting from protected, inactive bacteria will be required to replenish stocks of the pharmaceutical that have expired early because of space radiation.This renders crews independent from resupply spacecraft that could take at least 210 days to arrive after Earth launch.Moreover, the anticipated productivity rate should render the pharmaceutical production apparatus eminently portable and suitable for use on long voyages, because the required bioreactor working volumes need only be around 2 l or less.According to Stoker, this volume in a 3 l bioreactor would draw about 43.7 mW.A calcareous soil with low organic matter content was collected, air-dried and sieved through a 5-mm screen.Sewage sludge was collected, air dried and grounded to about 5 mm granules, and applied as such to each soil according to the treatments.The soil and SS were analyzed for general characteristics, nutrients and heavy metals according to the standard procedures.The major soil and SS characteristics are showed in Table 1.Greenhouse pot experiments with the following treatments were conducted in a randomized complete block design with four replications: 1) zero SS application ; 2) 20 ton SS ha-1; 3) 40 ton SS ha-1; 4) 80 ton SS ha-1; 5) 160 ton SS ha-1; 6) 80 ton Cd-enriched SS ha-1; 7) 160 ton Cd-enriched SS ha-1; and 8) 80 kg DAPha-1 that represented the recommended fertilizer rate.The SS was enriched with Cd by addition of CdCl2 to a Cd concentration of 50 mg kg-1.Each pot was filled with 7 kg air dry soil, air dry soil-SS mixture or air dry soil fertilized with DAP per treatments.Three radish seedlings per pot were planted in seven-liter pots.Plants were watered on alternate days to maintain water content at approximately field capacity.At the end of the growing period , the whole plants were harvested from each pot.

The fresh weights of both shoots and tubers were recorded.Plant parts were oven-dried at 700C for 48 hours, then dry weights recorded.Plant parts were ground to a fine powder using a laboratory mill with 0.5 mm sieve.The milled plant samples were analyzed for nutrients and heavy metals by standard procedures.The soil at the end of the experiment was analyzed for the same parameters mentioned above.Addition of original and Cd-enriched SS increased shoot N content compared to both control and DAP fertilizer treatments.All rates from 40 to 160 ton SS ha-1 of both original and Cd-enriched SS gave the highest shoot and tuber N contents with no significant differences among each treatment.The tuber N content was the lowest for the DAP fertilizer treatment and was even lower than that of the non fertilized control treatment; possibly this decline could be attributed to the dilution effect caused by the higher growth with DAP fertilizer application.Shoot P content increased with increasing rates of SS and was the lowest for the control,dutch buckets system and then the DAP fertilizer treatments.Tuber P content was higher with SS application being the highest with higher rates of SS.The lowest tuber P content was obtained with the control treatment and the DAP fertilizer treatment gave a value higher than that obtained by the control and the SS rate of 20 ton ha-1.Both shoot and tuber K contents were not affected by SS application except by the highest rate of the Cd-enriched SS which might attributed to the increased concentration caused by the stunted growth.Increased plant concentrations of N, P and K with SS application is mainly attributed to the increased levels of the available forms of these nutrients in the soil following SS application.Moreover, Oudeh et al.reported that sludge contains large amounts of N and P, and found an increase in their levels in SS-treated soil when compared to a control or even to the chemical fertilizer treatments.It should be mentioned however, that excessive application of N and P by high rates of sludge application can be detrimental to crop production and the environment.On the other hand, other researchers reported that little differences were found between Thissue concentrations of N, P, and K in corn grown on SS amended soil versus the control.However, it has been reported by Rubin et al.that applying SS at a rate sufficient to meet the plant’s N requirement would provide an excess of P but insufficient K.Therefore, they stated that balancing the amount of nitrogen applied in the SS with the plant’s requirement is an important management factor to avoid nutrient imbalance.Shoot Fe concentration increased with application of SS at rates equal to or higher than 40 ton ha-1.The highest two application rates resulted in lower shoot Fe when the SS was enriched with Cd.Similar trends, but with lower values, was obtained for tuber Fe concentration.Concentrations of Mn in the shoot increased with SS addition, with the highest values obtained by the highest two rates.The treatments effect on tuber Mn concentration was not significant.Application of SS at rates equal to or higher than 40 ton ha-1, similarly or equivalently increased both shoot and tuber Zn concentrations over other treatments.Addition of 80 and 160 ton ha-1 of SS, with or without Cd enrichment, resulted in the highest Cu concentrations in both the shoot and the tuber of radish.The highest shoot Cd concentration was obtained with the application of the highest rate of the Cd-enriched SS followed by the next highest rate.Application of original SS increased shoot Cd only at the highest rate of 160 ton SS ha-1.A similar trend was observed with tuber Cd concentration.SS may facilitate higher mobility for heavy metals through the effect of dissolved organic compounds from the applied SS that form soluble complexes with Cd and Zn and to a lesser extent with Cu and Pb.It is well documented that most of the heavy metal accumulation occurs in the roots of vegetable crops.Differences between root and leaf content was larger for Cd than for Pb, indicating that the translocation of Pb from roots to leaves is more limited than for Cd.

Frost and Ketchum found higher Cd in leaves with SS application.On the other hand, Oudeh et al.found that Zn and Cu but not Cd concentrations were higher in roots than in shoots.In this study, such a differentiation in Pb and Cd distribution were not observed.DTPA-extractable Fe, Mn, Zn and Cu increased with increasing SS application rates.Addition of 160 ton of both SS and Cd-enriched SS ha-1 resulted in the highest values for DTPA-extractable micro-nutrients.On the other hand, DTPA-extractable Pb increased similarly by all rates of SS application rates.Both the control and the DAP fertilizer treatments resulted in the lowest values of the DTPA-extractable Pb.Addition of the Cden riched SS resulted in the highest DTPA-extractable Cd being higher at the higher application rate.Comparatively, much lower DTPA-extractable Cd levels were obtained for the application of the original SS.However, the highest two rates of the original SS yielded higher values of DTPA-extractable Cd compared to the lower rates, but the highest levels of Cd were found with the addition of the Cd-enriched SS.The relationships between the DTPA-extractable Cd and the Cd concentration in radish shoot and tuber were significant and followed quadratic equations.The Cd concentration tended to slowly increase with increasing DTPA-extractable Cd within the range from 0.05 to 0.15 mg kg-1, after that a steep increase was observed.It can be summarized that application of SS to calcareous soil improved soil organic matter, available P, and micro-nutrients as well as the plant growth.However, application of higher rates was unnecessary for plant growth and yet has the potential to cause nutrient imbalance in the soil.Cd-enriched SS resulted in stunted growth at the highest rate and tend to accumulate Cd in the soil and plant parts.Therefore, it can be concluded that SS application to calcareous soils improves plant growth and soil fertility but at high rates of SS and SS rich in Cd should be avoided.