Our team had a sudden question because of a bowl of freeze-dried instant noodles: "we all feel that there is no nutrition when we eat freeze-dried noodles. Is it not 'nutritional emo' for astronauts to eat for a long time? ”After checking the data, we found that the prepackaged food of the international space station (ISS) is not only monotonous, but also the activity of whey protein will drop by 30% after 6 months of storage, and astronauts will also face problems such as muscle loss. They are in urgent need of a highly active and suitable human protein, which becomes the trigger for our project.

NASA's low earth orbit transportation cost is about $10000/kg. The cost of protein supply for three people on a Mars mission for 180 days will exceed 2million dollars. Moreover, the non-recyclable prepackaged food will also generate space waste. From this, we hope to use CO₂ exhaled and urine excreted by astronauts as raw materials for protein synthesis -- "closed-loop circulation".

Why hydrogen bacteria?

At first, we considered using cyanobacteria, but it needs stable light, which will increase energy consumption, and it cannot use hydrogen produced by electrolyzing water. Later, we found the Cupriavidus necator H16. It perfectly matches the existing resources of the space station and has become our "exclusive chef in space" without any suspense.

Why α-lactalbumin?

We initially considered bovine serum albumin, but the amino acid ratio of bovine protein was 20% lower than that of human protein. Later, after browsing the database, we found that α-lactalbumin: it accounts for 22% of human milk protein, and its branched chain amino acid is 1.5 times that of bovine origin -- this can resist muscle loss, its tryptophan content is high -- this can relieve the pressure of space, its dissipation rate is more than 90% -- this can adapt to the low functional state of the stomach in space, and even its molecular weight is only 14kDa, which is simple in structure and easy to synthesize. Therefore, α-LA has become our "ultimate recipe".

1.Engineered the hydrogen-oxidizing bacterium Cupriavidus necator H16 to directly convert astronaut waste streams into high-value human alpha-lactalbumin inside spacecraft.

2.To design a bioreactor capable of operating within a space station, incorporating microgravity control, temperature control, and microbial containment.

3.We will share the optimized expression system for C. necator H16, autotrophic fermentation parameters, and metabolic models to support future research focused on in-situ resource utilization and biomanufacturing in extreme environments.

4.Engage the public across different age groups through various activities to introduce the concept of space biomanufacturing, while collecting societal feedback and acceptance levels regarding our technology, ensuring that scientific development progresses in tandem with public dialogue.

We selected the hydrogen-oxidizing bacterium Cupriavidus necator H16 as our chassis and the pBBR1 plasmid as our vector. By introducing the exogenous hLALBA gene, we enabled the strain to express human alpha-lactalbumin. Furthermore, using CRISPR-Cas9, we knocked out key competitive metabolic pathway genes—areA,gcl,put, and hut—reprogramming the strain’s metabolic network to channel resources efficiently toward target protein synthesis.

Our engineered strain does not rely on organic carbon sources. Instead, it grows using hydrogen gas as the electron donor, carbon dioxide as the carbon source, and oxygen as the electron acceptor. The gas mixture was optimized at a ratio of H₂ : O₂ : CO₂ = 7 : 2 : 1. Initially, a small amount of ammonium sulfate was supplemented as the nitrogen source. Subsequently, we conducted autotrophic tests using urea as the sole nitrogen source, demonstrating the feasibility of utilizing nitrogen recovered from urine treatment systems in a space environment. Hydrogen and oxygen can be supplied via water electrolysis, while CO₂ is sourced from astronaut respiration, achieving in-situ recycling of key resources.

We designed a gas fermentation system specifically optimized for microgravity conditions. To maximize gas-liquid contact efficiency under microgravity—where liquids form floating droplets—a multi-layer stainless steel packing structure was incorporated to provide surface area for droplet attachment, significantly increasing the gas-liquid interface. The reactor is integrated with pH and dissolved oxygen sensors to maintain optimal growth conditions. To enhance operational safety, a flexible soft-pack material was adopted instead of a rigid reactor vessel.

To further improve the nutritional value of the product, we rationally designed an ideal trypsin cleavage site into the alpha-lactalbumin gene sequence. This modification aims to promote more precise and efficient digestion of the protein in the human gastrointestinal tract, increasing the release of highly absorbable di- and tri-peptides, thereby maximizing its nutritional efficacy.

Looking ahead, we aim to expand the biosynthetic capacity of our chassis organism beyond α-lactalbumin to include functional proteins such as lactoferrin and globulins, as well as essential metabolites like branched-chain amino acids and tryptophan. This will enable personalized nutrition tailored to astronauts’ needs during different mission stages.

In parallel, metabolic engineering will be applied to produce vitamins (e.g., D, K, and B-group) and cofactors, reducing reliance on external supplementation. We also envision integrating with probiotics, using surface anchoring or co-culture systems to combine nutritional output with gut health benefits.

In the longer term, the chassis bacterium would be capable of producing not only nutrients but also bioplastics and pharmaceutical precursors to help astronauts withstand radiation and oxidative stress, thus providing comprehensive support for future deep-space missions.