Mars shelter problem can be solved with engineered yeast: paper

Future settlers on Mars would need houses, but they must either spend huge sums transporting construction materials from Earth or use enormous amounts of energy to melt Martian soil into bricks.

Scientists in Hong Kong say they have developed a quick and low-cost “living” building material made from genetically engineered yeast, gelatin and sand that can be 3D printed under conditions simulating the Martian environment.

Their study, published online last month in Chem Circularity, an international Cell Press journal, describes a biological binder that holds granular materials together.

The optimised formulation had a compressive strength of about 12 megapascals (MPa), around 170 per cent higher than that of the control formulation and within the range of conventional building materials.

The material was developed by Professor Qiu Jishen and his team at the Hong Kong University of Science and Technology and scientists from Hong Kong Polytechnic University.

“This is an important research direction,” said Zhu Xiaohong, a professor of building materials at Beijing University of Technology who was not involved in the study.

Building on Mars is difficult because many existing approaches require minerals to be processed at temperatures of about 1,000 degrees Celsius (1,832 Fahrenheit), consuming large amounts of energy and requiring heavy equipment.

The Martian atmosphere is less than 1 per cent as dense as Earth’s, while surface temperatures can fall below minus 50 degrees.

The scientists’ building material consists of sand or other granular particles, a gelatin hydrogel and engineered yeast, with the yeast surface modified to display adhesive proteins.

The team used proteins, including mussel foot proteins, to strengthen the links between the yeast cells, the gelatin binder and the aggregate particles, according to the paper.

“As long as enough high-strength adhesive proteins have been produced before the yeast enters dormancy, this does not affect the load-bearing capacity of the building,” Qiu said.

The material hardens during freeze-drying, as water in the mixture changes phase under low pressure, leaving behind a porous gelatin scaffold with yeast cells embedded in its walls.

The engineered yeast helped to create a more uniform pore structure and strengthened the material.

The researchers also used the material to 3D print a small beacon-like structure inside an environmental chamber at 0.01 atmospheres and minus 30 degrees, conditions designed to simulate the Martian environment.

The printed structure was 45mm (1.8 inches) high and 30mm in diameter.

The researchers estimated that producing 1 cubic metre (35 cubic feet) of the biological material would require less than an hour of solar-panel operation, compared with several days to sinter the same volume of Martian regolith into a solid block.

The material could also be remanufactured. After being crushed, rehydrated and gently heated, the gelatin-based composite could be processed again, with fourth-generation samples retaining a compressive strength of about 11.8 MPa.

But the material still depends on supplies from Earth.

Qiu said the team estimated that producing 1 cubic metre would require only tens of kilograms of raw materials supplied from Earth, with about 70 to 80 per cent of the mass consisting of gelatin and the remainder comprising nutrients for the yeast.

“If methane, carbon dioxide and water ice on Mars can be converted into organic gelatin or nutrients, then in theory this number could become zero,” he said.

He added that most of the hundreds of tonnes of cargo required for a meaningful construction operation would instead consist of equipment such as solar panels or potentially small nuclear power systems.

The team also sees possible applications on Earth.

“We have indeed considered using it to build Antarctic research stations far from the coast,” Qiu said, noting that the greater gravitational load on Earth would limit the number of storeys that could be built compared with Mars.

Qiu and his team described the current material as a structural component rather than a complete habitat.

Zhu sees possibility in the project.

“I think its applications are certainly not mature yet, but the direction is worth studying, and I think there is potential for application,” he said.