Photobioreactor

Objectives

On Earth, the production of oxygen from carbon dioxide is ensured by photosynthesis, whether in microalgae or higher plants, which also potentially produces edible biomass such as vegetables and fruit. Within the MELiSSA loop, this function is performed by the photosynthetic compartments, with a clear intensification in the photobioreactor, compartment IVa.

Arthrospira platensis (commonly known as Spirulina) was chosen for its light-energy conversion efficiency, its high-pH environment that reduces contamination risk, and its high nutritional value. This deceptively simple microorganism is also genetically robust and able to adapt to a wide range of culture conditions, including space radiation.

Arthrospira platensis (Spirulina), the cyanobacterium at the heart of the photobioreactor compartment.

Challenges & Approach to the Research

Research on Arthrospira growth has shown that its metabolism is governed mainly by light-energy availability, so growth is ultimately limited by the light-energy flux inside the reactor.

Sustained progress has produced results such as 80 litres of microalgae culture supplying one person’s oxygen needs. These achievements have, in turn, driven real breakthrough innovations, including the use of optic fibres or thin-plate technology to optimise the photobioreactor’s volumetric productivity.

A thin-plate photobioreactor panel using optic-fibre light distribution to improve volumetric productivity.

Flight Experiments

Enabling oxygen production and a food supplement during spaceflight requires the technology to function reliably in the space environment. A representative version of the process, called ARTEMISS, was installed on board the International Space Station for several weeks.

This experiment provided results on the growth of the cyanobacterium Arthrospira sp. and the oxygen production associated with it.

Open view of the ARTEMISS flight hardware. The lighting system of the photobioreactor is visible.

Ground Demonstration

Long-term demonstration of a highly robust photobioreactor led to the construction of an 80-litre pilot reactor at the MELiSSA Pilot Plant, with fully controlled oxygen and biomass production.

The 80-litre pilot photobioreactor at the MELiSSA Pilot Plant, Barcelona.

This system has been operated with the objective of supplying oxygen and removing carbon dioxide for the Pilot Plant’s Crew Compartment. The long-term demonstration was carried out without any gas buffer.

Monitoring and control station for the photobioreactor unit at the MELiSSA Pilot Plant.

Terrestrial Applications

AlgoSolis. Building on MELiSSA’s results, the GEPEA laboratory (a joint research unit of the University of Nantes, CNRS, Oniris and Ecole des Mines de Nantes) developed the AlgoSolis R&D facility. AlgoSolis provides the scientific and technological environment needed to develop optimised strains, processes and methods for industrial applications requiring mass-scale microalgae production.

A flat-panel photobioreactor of the kind developed for intensified microalgae cultivation, of the type used at facilities such as AlgoSolis.

XTU biofacade. The architecture firm XTU and its partners in the SymBIO2 consortium set themselves the goal of developing highly innovative technologies to capture the potential of microalgae for more sustainable cities. MELiSSA’s intensified technologies, particularly the planar thin-plate photobioreactors, are well suited to forming a highly productive “curtain-wall photobioreactor”, in effect a building’s actual facade.

These photobioreactors maximise the use of solar flux for both microalgae culture and temperature regulation, reduce water consumption for algae cultivation by nearly 90% compared with classic open-pond cultures, and reach a volumetric productivity around 30 times higher than open ponds.

Artistic view of a biofacade building using curtain-wall photobioreactors, currently in construction in Paris.

EzCOL. As part of its search for food ingredients, the MELiSSA project tested a photosynthetic bacterium that proved safe and nutritious and, remarkably, was shown to reduce levels of LDL cholesterol, the “bad” cholesterol. With ESA’s support, the spin-off company EzCOL BV was set up by IPStar BV, MELiSSA’s technology-transfer partner, to continue researching and market the cholesterol-reducing bacterium.

INSPIRATION, DR Congo. The INSPIRATION project (INtroduction of SPIRulina in equAToRIal Africa to Improve lOcal Nutrition) was conceived and developed to support the cultivation of the cyanobacterium Spirulina in African communities. Spirulina is highly nutritious and can make an important contribution to the fight against chronic malnutrition, which currently affects 43% of all children under five in DR Congo.

A low-cost photobioreactor for local protein production, INSPIRATION project, DR Congo.

Education & Communication

Schools across Europe signed up for the “Food from Spirulina” biology experiment, in which students aged 14 to 16 carried out their own investigation of the cyanobacterium Arthrospira platensis, better known as Spirulina.

As part of ESA astronaut Samantha Cristoforetti’s education and outreach programme, ESA Education, working with ESA and MELiSSA scientists, developed an experimental kit for use in the classroom. Read more about the in-flight call with Samantha Cristoforetti on the ISS.