Powered by sunlight, scientists investigate a marine microalga that could contribute to a more sustainable bioeconomy

27.06.2023

Just like other photosynthetic organisms, microalgae evolved multiple mechanisms involved in the regulation of photosynthesis according to the availability of light, with the aim of surviving in a highly variable natural environment.

Under light-limiting conditions, photosynthesis maximizes the capture of light and its use. While under an overly abundance of light, photosynthesis dissipates the excess light to avoid photo-damage and death.

Researchers from the University of Padua, in collaboration with the University of Berkeley (California), published the study Modulation of xanthophyll cycle impacts biomass productivity in the marine microalga Nannochloropsis in PNAS (Proceedings of the National Academy of Science). Coordinated by Giorgio Perin and Tomas Morosinotto of the University of Padua Department of Biology, the study demonstrates that microalgae photosynthesis and its ability to remove CO₂ can be improved to make their cultivation more competitive in the marketplace and maximizing the production of biomass - the organic matter specially treated for use as biofuel.

The xanthophyll cycle is one of the mechanisms for regulating photosynthesis and involves the reversible transformation between two oxygenated pigments – xanthophylls – called violaxanthin and zeaxanthin.

Violaxanthin promotes the capture of light and is therefore favored in low light conditions, while zeaxanthin promotes the dissipation of excess light and is therefore favored in abundant light conditions.

Beyond their important ecological role, microalgae also represent a versatile source of biomass converted into multiple products, such as cosmetics, pharmaceuticals, food additives, animal feed, fertilizers and biofuels. Powered by sunlight, such microalgae could therefore contribute to the development of a more sustainable bioeconomy, thanks to its ability to sequester atmospheric CO2, currently responsible for global climate change.

Tomas Morosinotto, corresponding author and professor in Biochemistry at the Biology Department at the University of Padua explains, “Thanks to genetic engineering, we accelerated the conversion rate of zeaxanthin to violaxanthin in the marine microalgae of the genus Nannochloropsis, demonstrating that this strategy may improve biomass productivity. Our work shows that the xanthophyll cycle of microalgae is necessary for their well-being even during industrial cultivation and that the operating speed that this photosynthesis regulatory mechanism has evolved in nature represents an excellent target for microalgae domestication and improved productivity in photobioreactors.”