Algae and the chocolate factory

Extremophile algae that thrive in acidic hot springs could be ideal industrial partners for supporting sustainable manufacturing. These tough and versatile species can be grown in the dark, fed on a wide range of organic wastes, and are especially productive when grown in an environment spiked with CO₂, KAUST researchers have shown^[1].

“Galdieria’s evolution in hot, corrosive volcanic pools has equipped it to colonize new habitats few other organisms can handle,” says Mauricio Lopez-Portillo Masson, a Ph.D. candidate in the lab of Kyle Lauersen, who led the research. “Galdieria can be found in industrial waste sites with high dissolved gases, high temperatures, and acidic conditions, in addition to their native hot springs,” Lopez-Portillo Masson adds.

“Resilient and metabolically flexible, Galdieria can switch between photosynthesis and feeding on glucose or other organic molecules to meet its energy needs, which has sparked industrial interest,” Lauersen explains. As it grows, Galdieria produces a rich, balanced blend of essential amino acids, suggesting potential as a novel food or high-quality livestock feed. The alga also produces a blue pigment called phycocyanin, with applications as a natural blue food coloring, a cosmetic ingredient, and an antioxidant nutraceutical.

As Galdieria’s natural environment is in acid hot springs, its phycocyanin is heat- and acid-stable, and thus well-suited for industrial food pasteurization or cosmetics production. “Because Galdieria can eat many carbon sources and can be grown in fermenters like those used for brewing, the field’s long-term goal is to use Galdieria to turn sugar or other organic carbon into this valuable blue pigment,” Lauersen says.

In collaboration with Peter Lammers at Arizona State University, the team identified a Galdieria strain from Yellowstone National Park, Galdieria yellowstonensis, that reliably produces photosynthetic pigments, including phycocyanin, even when fed a glucose diet. The next step was to find the ideal conditions for growing these unusual microbes at scale.

While screening potential conditions, the team discovered that spiking the fermentation tank with CO₂ significantly boosted Galdieria’s growth. That result might be expected when the alga is grown in the light and consuming CO₂ during photosynthesis, but the team recorded the same boost even when Galdieria was grown on glucose in the dark.

Working with Michael Fox and KAUST’s Core Labs, the team used stable-isotope measurements to confirm that CO₂ acts as a trigger, rather than being incorporated into the alga’s biomass. These growing conditions may resemble the CO₂-rich environment in hydrothermal vents where the species evolved, Lopez-Portillo Masson says. “It’s as if the cells recognize that they’re ‘home’ when CO₂ levels are high.”

Testing the CO₂-enriched growth conditions in a real-world example of circular waste management, the team showed the alga happily consumed confectionery waste from a local Mars chocolate bar factory, generating phycocyanin-containing Galdieria biomass.

Other industries generate much more carbon waste than the 20 tons generated annually by the chocolate factory, Lauersen adds. “Glycerol is also a preferred Galdieria food: in the kingdom, some companies produce hundreds of tons of waste glycerol per month.

“From existing local waste streams, we could grow 150 tons of algal biomass per month, which can be used for animal feed, cosmetics, pigments, and many other applications,” Lauersen says. Such resource circularity aligns with the Saudi Vision 2030 goals and is within the Kingdom’s Research, Development, and Innovation Authority (RDIA) strategic pillars for Sustainable Environment and Essential Needs, as well as Economies of the Future.

Reference

1. Lopez Portillo Masson, M., Bastos de Freitas, B., Zybinskii, A., Althagafi, G., Amad, M., Fox, M.D., Lammers, P.J., Lauersen, K.J. Elevated carbon dioxide stimulates efficient organic-carbon consumption for the unicellular alga Galdieria. Trends in Biotechnology, advance online publication (22 November 2025). | article.

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