Bioregenerative Dietary Supplementation: Optimizing Brassica Production for Space Travel Through Light Intensity, Photoperiod, and Harvest Methodology

Bioregenerative dietary supplementation, a component of bioregenerative life support, will be necessary for the success of future exploration-length space endeavors. Plants, as autotrophic producers of calories, nutrients, and oxygen, will be indispensable in the development of these systems. Previous work has identified leafy greens from the genus Brassica as promising candidates for in-flight production of necessary human nutrients such as vitamins C, B₁, and K₁, in addition to β-carotene, the primary vitamin A precursor in the human diet. These plants also produce lutein and zeaxanthin, two compounds important in protecting the eye from radiation-induced damage, as well as a variety of anthocyanins which act as general antioxidants in the human body, potentially decreasing the damaging effect of free-radicals. Finally, plants accumulate minerals in their tissue, including calcium, potassium, magnesium, and iron; all of which have important implications in the diet of space-faring humans. This thesis seeks to determine 1) which cultivars of Brassica (selected from three species within the genus) produce the most promising phytonutrient and morphological profiles for production in space, 2) how light intensity and photoperiod can be manipulated to increase these phytonutrient concentrations, and 3) how a continuous or ‘cut-and-come-again’ harvest strategy can be implemented to maximize phytonutrient yield efficiency. This was tested by growing plants in a controlled environment growth chamber emulating the temperature, humidity, and CO₂ concentration aboard the International Space Station (ISS), and performing a series of phytonutrient extractions and quantifications on the resulting tissue. Of the cultivars evaluated, B. carinata ‘Amara’ provides the strongest phytonutrient profile, an aspect of which was the notable production of higher vitamin B₁ concentrations than any cultivar of B. rapa var. nipposinica. A high light intensity, 800 µmol⋅m^-2⋅s^-1, applied across a 16-hr photoperiod further optimized the profiles of this cultivar and of a complementary cultivar, B. rapa var. nipposinica ‘Red Hybrid’, for space production. Finally, a continuous harvest protocol increased the phytonutrient production per day per unit of production space when compared to a single harvest approach, and these gains increased over subsequent harvests.