3-D Printed Corals, New Bioreactors to Boost Microalgae Production for Biofuels

by Fintan Burke (Horizon Magazine/Phys.Org) Using light as an energy source, photosynthetic microalgae can be used to produce products like biofuels and cosmetics. But algae grown in a reactor block out the light on which they feed. New reactor designs could solve this problem and help the industry move forward.

Photosynthetic algae—tiny algae that use light to grow—offer an alternative to traditional fossil fuels. The small amount of lipids each cell produces can be harvested to produce biofuel for the transport industry.

Currently, there are two main designs to grow the algae: either through an outdoor artificial 'pond' or through a closed 'photobioreactor' – usually a transparent tube or bag.

Both have their problems. Although an open pond can be big enough for industrial production, it is difficult to control the pond's temperature and the water can easily get infected with unwanted bacteria.

An indoor photobioreactor reduces both these risks, but few designs can be used for industrial production. In both types, the photosynthetic microalgae begin to block out the light as they grow.

Dr. Wangpraseurt and his BioMIC-FUEL project took inspiration from how microalgae grow on tropical coral reefs. By recreating coral structures, he and his team hoped to recreate the best conditions for biofuel production.

As Dr. Wangpraseurt explains, these corals have a unique structure that allows photosynthesising algae to thrive in an environment with a lot of competition for space and light. For example, the coral skeleton is made from calcium carbonate, which allows the coral to scatter light in a way that it can reach dense microalgae growing on it.

The next step was to create a 3-D printing technique that could replicate the shape of corals, including their unique light-scattering chemical structure. This involved working with bioengineers with expertise in 'printing' cells in artificial organ research.

Right now, businesses looking for an indoor bioreactor still have few options—the technology still runs into problems such as controlling the light and nutrients in the reactor, and minimising contamination risk.

Brevel's bioreactor design uses patented lighting and cleaning techniques to illuminate the photobioreactor inside while reducing the risk of infection by bacteria. The new lighting techniques mean that light in the reactor can be both smaller and brighter, without heating up the bacterial mixture. Digital image analysis and online monitoring means that the Brevel photobioreactor is also more automated than other photobioreactors available to industry. READ MORE