3D Printed Corals Could be Used to Farm Algae Biofuels

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With global warming causing sea temperatures to rise, the coral reefs are dying around the world. The delicate reefs are particularly susceptible to even small changes in average temperature and salinity, and as they die, this could also spell disaster for the many marine organisms that call the reefs home. This has led researchers to come up with various solutions, and one of the most promising may be printing 3D replacement reefs.

While 3D-printed coral cannot bring back the living coral, it could help to reinvigorate some of the ecosystems that use the reefs. But its primary use could be in the growth of marine biofuels.

The importance of corals

Corals form a major component of a number of tropical marine ecosystems. Without their presence, the food chains in these systems break down. For example, certain types of microalgae live in a symbiotic relationship with corals. The corals provide a surface for the microalgae to grow, and in return, the algae produce food for the coral.

This microalgae also happens to be an energy-rich biofuel.

This has inspired Dr. Daniel Wangpraseurt, of Cambridge University, to develop an artificial coral structure for the algae to grow on, so it can be harvested to create biofuel.

"Corals are highly efficient at collecting and using light. In our lab, we're looking for methods to copy and mimic these strategies from nature for commercial applications.

Dr. Wangpraseurt's co-researcher, Dr. Silvia Vignolini, had this to say about the project:

"We developed an artificial coral tissue and skeleton with a combination of polymer gels and hydrogels doped with cellulose nanomaterials to mimic the optical properties of living corals. Cellulose is an abundant biopolymer; it is excellent at scattering light and we used it to optimize the delivery of light into photosynthetic algae."

Both researchers are trying to maximize the growth potential of microalgae called Marinichlorella kaistiae. This particular algae produces fatty acids that are incredibly energy-rich. The algae grow on Pocilloporidae corals, so the team 3D-scanned these corals in order to develop a blueprint for the 3D-printed coral forms.

The development of artificial corals

In more precise terms, the cupped shape of the coral collects and focuses light in areas where the algae grow. In particular, the coral is efficient at focusing the blue and orange wavelengths of light which the algae need for photosynthesis.

"By copying the host microhabitat, we can also use our 3D bioprinted corals as a model system for the coral-algal symbiosis, which is urgently needed to understand the breakdown of the symbiosis during coral reef decline," said Wangpraseurt. "There are many different applications for our new technology.

We have recently created a company, called mantaz, that uses coral-inspired light-harvesting approaches to cultivate algae for bioproducts in developing countries. We hope that our technique will be scalable so it can have a real impact on the algal biosector and ultimately reduce greenhouse gas emissions that are responsible for coral reef death."

As noted by Dr. Wangpraseurt, algae growth isn't just good for biofuel production, it also is a major consumer of greenhouse gases. Finding a way to scale algae production could create a massive carbon filter for the surrounding areas.

3D Printed Corals Could Be the Future of Bioenergy — Colony of the coral Stylophora pistilla growing at about 10 m depth on Watakobi Reef, East Sulawesi, Indonesia (a). Close-up photograph (**b, c**) and optical coherence tomography scanning (**d, e**) of coral skeleton and coral tissue, respectively. Scanning electron microscopy image of successful 3D printed skeleton replica showing corallites in 1:1 scale relative to the original design (f). Photograph of living bionic coral growing Symbiodinium sp. microalgae (g). The living tissue was printed on top of the skeleton mimic and the bionic coral was cultured for 7 days. Scale bar = 1 mm (b–f) and 750 µm (g). Source: Nature

One of the biggest problems the researchers faced is that the Marinichlorella, the microalgae, die in the process of transferring them from their host culture onto the artificial corals. However, through a unique bioprinting technique, the researchers were able to plant the algae on the surface of the new fake coral during the manufacturing process itself.

Another benefit to the artificial coral is that they provide a better growing surface for the algae than the real coral. The researchers were able to engineer the artificial coral shapes to be more efficient at capturing light, providing a more photon rich environment for the algae to grow.

When compared to the natural coral, the new coral structures allow the microalgae to grow 100 times faster, and in a denser mat, than in any other area where they have been cultivated, both in the lab and the sea.

The biggest problem for the team right now is scalability. For anyone familiar with the process of additive manufacturing, you likely realize that it isn't the best system for mass production. However, in this case, the team has no other option for producing its artificial coral. They're hopeful that new innovations in the additive manufacturing space will help them further speed up their production process down the line.

Their research is published in Nature Communications.