Food and other products can be produced using industrial biological processes. This makes otherwise complex foods more accessible, it makes foods cheaper to produce and it simplifies the production of the industrial materials required for civilization.
Methanotrophs such as Methylococcus capsulatus can use methane and methanol as both a source of energy as well as a carbon source. Using a Sabatier reactor, nuclear power can be used to convert atmospheric CO2 into food or other biomass through biological processes. To grow, these methanotrophs also require Nitrogen, Sulfur, Phosphorous and various trace metals. Nitrogen can be captured from the Martian atmosphere, by allowing the Methanotrophs to grow in an anoxic atmosphere and nitrogen fix for themselves, or through a Haber reactor on refined atmospheric nitrogen producing ammonia. Sulfur and phosphorous are accessible in the regolith and will be released through metal processing. Other trace metals are only needed in minute amounts to operate enzymes and are easily recycled. These microbes are currently used on Earth to produce animal feed, and their use in human food production is an active area of biotechnological research. The growth yields of methanotrophs have been extensively studied, with Methanol/Nitrate feedstock with trace amounts of Copper shown as an optimal point, with lower yields but higher carbon conversion efficiencies than other feedstocks. Colonies could potentially use Methanotrophs as a foodstuff utilizing nuclear power in the nuclear food cycle, or solar power electricity, which may be considerably more compact or easier to deploy than greenhouses or other conventional farming methods.
Grass to glucose
Traditional hydroponic farming is complex and labor intensive. In contrast, growing and harvesting large grasses such as Miscanthus Giganteus is simple to do in a large scale and automated way through cellulose farms. These grasses can then be broken down via cellulases to provide an accessible source of glucose, along with other industrially useful compounds such as THF (a common solvent).
Syngas to biomass
Syngas, produced through either recycling carbon containing compounds through pyrolysis or directly from CO2 and water, can be used to produce biomass. Organisms such as Clostridium carboxidivorans can directly metabolize syngas as a source of energy and carbon, forming industrially useful compounds such as ethanol, acetic acid along with medium chain (C4/C6) fatty acids and alcohols. Alternatively, syngas can also be used to produce methanol or methane which can be fed to Methanotrophs.
Some organisms, such as Rhodopseudomonas palustris have a versatile metabolism, and so can consume a wide variety of chemicals both with and without sunlight in order to grow. It is capable of fixing both atmospheric CO2 and N2, and oxidising things as diverse as Iron, aromatic hydrocarbons or plant lignin as a source of energy. It has also been shown to be able to produce CH4 with a modified nitrogenase when grown on acetate/carbonate and exposed to light.
Biomass to industrial chemicals
Using GM microbes, biomass can be digested directly into a series of usable products such as Ammonia, short chain hydrocarbons, Adipic acid (a precursor to nylon), Phenol (a precursor to plastics) , or converted to Benzene/Xylene/Toluene via catalytic reforming. This allows for greatly simplified industrial chemistry through a mix of careful genetic engineering and choosing biologically accessible industrial precursors.
Biomass to engineered foods
Using genetically modified yeasts, it is also possible to directly produce proteins such as those found in eggs or milk. It is also possible to produce various flavonoids, providing a variety of smells and flavors to artificially produced food. Vitimins and other essential nutrients can also be produced and added to ensure that foods are both tasty and nutritious.