An Electro–Microbial Process to Uncouple Food Production from Photosynthesis for Application in Space Exploration

Abstract

Here we propose the concept of an electro–microbial route to uncouple food production from photosynthesis, thereby enabling production of nutritious food in space without the need to grow plant-based crops. In the proposed process, carbon dioxide is fixed into ethanol using either chemical catalysis or microbial carbon fixation, and the ethanol created is used as a carbon source for yeast to synthesize food for human or animal consumption. The process depends upon technologies that can utilize electrical energy to fix carbon into ethanol and uses an optimized strain of the yeast Saccharomyces cerevisiae to produce high-quality, food-grade, single-cell protein using ethanol as the sole carbon source in a minimal medium. Crops performing photosynthesis require months to mature and are challenging to grow under the conditions found in space, whereas the electro–microbial process could generate significant quantities of food on demand with potentially high yields and productivities. In this paper we explore the potential to provide yeast-based protein and other nutrients relevant to human dietary needs using only ethanol, urea, phosphate, and inorganic salts as inputs. It should be noted that as well as having potential to provide nutrition in space, this novel approach to food production has many valuable terrestrial applications too. For example, by enabling food production in climatically challenged environments, the electro–microbial process could potentially turn deserts into food bowls. Similarly, surplus electricity generated from large-scale renewable power sources could be used to supplement the human food chain.

Reducing Carbon Intensity of Food and Fuel Production Whilst Lowering Land-Use Impacts of Biofuels

“…Conceptually, a biorefinery operating in the manner described could even provide the fertilizer needed to grow the biomass feedstock or the nitrogen source needed to grow yeast biomass within the process. The potential to grow yeast and other microbes as nutritious protein sources using basic carbon molecules plus urea and salts has recently been discussed by others [60] and demonstrated in our laboratory [45]. These advances open the way to consider biorefineries as an integrated source of microbial protein for food, plus chemicals including those for broader applications as fuels.…”

“…Although soybean is rich in dietary protein, it contains antinutritional factors, including phytates, tannins, trypsin inhibitors, and oligosaccharides that negatively impact, e.g., iron absorption [43,44]. High protein-containing yeasts can circumvent these antinutritional problems by providing the necessary amino acid balance, together with essential B vitamins and dietary fiber [45]. Moreover, S. cerevisiae produces phytase activities that can reduce iron binding issues associated with soybean meal [46].…”

Visioning synthetic futures for yeast research within the context of current global techno‐political trends

“…Engineered yeast will be essential to nutritional diversity in space, ensuring that a range of tastes, flavours, aromas (Van Wyk et al, 2018) and colours negate the risk of dietary fatigue. Altered carbon source utilisation will be essential to wholly circularise waste management on any resource‐isolated extraterrestrial destination (Bell et al, 2022; Espinosa et al, 2020). As yeast research and technology matures, it may be feasible within a few decades to produce a ‘colony starter kit’ consisting of a consortia of engineered yeast with pan‐genomic diversity through carefully selected neo‐chromosomes layered over minimal genome architectures.…”

Harnessing bioengineered microbes as a versatile platform for space nutrition

“…Furthermore, studies have shown that microgravity conditions do not seem to significantly affect its growth or viability 17 , and work conducted by NASA has highlighted the potential for engineered S. cerevisiae as a useful source of essential nutrients for human health and nutrition (e.g., NASA’s BioNutrients project). Recent estimates of the nutritional value of a vitamin-prototrophic yeast strain in the context of human space travel suggest that all vitamins and macronutrients necessary for a balanced human diet could be provided for 50–100 people per day from a single 3000 L fermentation 18 . All this makes S. cerevisiae a promising candidate for developing into a microbial food-production system (Fig.…”

“…Alternatively, a more mature technological possibility involves the electrochemical reduction of carbon dioxide with hydrogen to form methanol in a process already commercialized on Earth by the company Carbon Recycling International. Given that the yeast Pichia pastoris can grow efficiently on methanol (growth rate of 0.15/h) 25 , and there are strains of S. cerevisiae that can grow efficiently on ethanol made from a similar process 18 , the electrochemical reduction of CO 2 with hydrogen poses a promising solution to the recycling of waste carbon to food in a space-travel setting. Once these problems are solved, this process could become very attractive since liquid carbon sources are easier to store and are more easily utilized in a bioreactor.…”