One of the researchers' latest projects involves using living cells as mini-factories for producing a wide variety of valuable materials. The cells can be used for the automated cultivation of biomass in a bioreactor called PhotoBionicCell, which contributes to the increasing biologisation of industry, whose ultimate goal is to achieve a climate-neutral circular economy and reduce the ecological footprint.

"In the Bionic Learning Network, we have been looking into the circular economy of the future for a long time and thinking about how we could contribute to it," says Dr. Nina Gaißert, a biotechnologist in the bionics team. "We also wanted to work with living matter; so when we came across algae, which are perfectly suited to producing different substances depending on the species, we started to develop a bioreactor to combine living and technical components and produce new materials - such as foodstuffs, fuels or plastics - biologically."

Microscopically small algae - microalgae - live in the novel bioreactor in Esslingen. They are so frugal that all they need for healthy growth is a medium consisting of minerals and salts, water, light and CO₂. If these components are then made available to them in exactly the right proportions using control and automation technology, the green mini-factories not only produce a huge amount of biomass as a starting material for other valuable substances in our everyday lives, such as fatty acids, colour pigments or surfactants, but they also fix a hundred times more CO₂ than terrestrial plants – whilst requiring considerably less land and water than their land-dwelling relatives. In addition, most of the biobased end products can be biodegraded.

The manual component, which is still required for most laboratory work today, is no longer needed; this minimises sources of error and saves time and money: the technical solution developed at Festo for this purpose consists of a fully automated 24-hour algae growth monitoring system, which is as perfect as the microorganisms could ever have in any body of water in the world. For this purpose, the experts developed extensive sensor technology to be able to record, for example, the optimal pH value, the nutrient ratio or the number of algae and the growth rate in the bioreactor. "It is impossible to determine with the naked eye which life cycle the algae are in and whether they are doing well," explains Gaißert. "But the sensor technology allows us to do just that, and that's why the algae can grow as efficiently as possible in the PhotoBionicCell."

A permanent supply of CO₂ is essential for the algae to optimally photosynthesise. This is provided by a specially developed aeration element that draws in the ambient air containing huge amounts of CO₂ by pumping the algae liquid upwards into the collector arrays and subsequently atomising the air into bubbles to create the largest possible reaction surfaces.

What at first glance looks complicated is actually quite simple: for the bioreactor, which laypeople could easily mistake for something akin to a small spaceship combined with a hot-air balloon, an intuitive interface was created that allows users to access all process data and sensor values in real time on a website and thus, for example, find out the optimal harvest time. Artificial intelligence methods are also employed here to produce the best possible environment for algae growth. "Theoretically, you could also access the data from your home office and, if necessary, initiate the harvest immediately," says the scientist. Another tool, an augmented reality app, enables all sensor values to be viewed in real time. This requires only a single fixation with the smartphone - almost as if the user were taking a photo of the reactor.

An algae species called Synechocystis is currently being cultivated in Festo's bioreactor. "We chose this microalgae species after carrying out algae database searches to find a species that is able to produce plastic – in particular the biopolymer polyhydroxybutyric acid PHB," says Gaißert. "But this can be done just as effectively with other algae, such as spirulina. It simply depends on the desired application. In principle, everything that is currently produced from petroleum can be synthesised. However, it is not yet economical enough. What would work well, however, are high-value algal products such as pharmaceuticals."

Plastic production has already worked very well in Esslingen: the researchers were able to extract PHB from Synechocystis cultures and, by adding other substances, be processed into a filament for 3D printing and for packaging material and used, for example, to produce a mounting bracket for the reactor. However, Festo is not considering producing this type of plastic itself: "Our speciality is the reactor drive, supplying the control and regulation technology for the reactor," says Gaißert. "Of course, we would like to scale up the reactor from the current 15 l to a much larger scale, but Festo has no plans to build these devices. For that we would need industrial partners."