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Blue diatoms are unique among marine microalgae because, as they grow and age, they can produce large amounts of marennine, a water-soluble bluish pigment. When released into seawater, this pigment turns oysters green. "Known for their special taste and colour, green oysters, are 15-20 % more expensive than ordinary oysters," explains BIOVADIA project coordinator Jean-Luc Mouget. "Today, these oysters have a positive economic impact in western France and for centuries, they were very much appreciated by French kings, in particular Louis the 14th," he adds.
But it's not just its popularity among French kings that makes the pigment valuable. Not only could marennine from the blue diatom Haslea ostrearia and other members of the genus be used as a natural biodegradable blue pigment in the food industry, but its antimicrobial and anti-inflammatory characteristics also make it a potentially soothing ingredient in medical creams and cosmetics. "In fact, marennine could also function as a natural antimicrobial compound in aquaculture, also known as aquafarming, to prevent the misuse and overuse of chemical antibiotics," says Mouget. If scientists can mass-produce this type of rapidly growing phytoplankton, it could even have applications in agriculture as an animal feed or supplement.
Biodiversity of Haslea - discovering new species
"For decades, scientists believed that Haslea ostrearia was the only diatom producing marennine-like blue-green pigment. The BIOVADIA project was groundbreaking because it demonstrated that this is not the case," reports BIOVADIA project co-lead and work package manager Rupert Perkins. The project discovered five new species of blue Haslea, and described the characteristics of two of them - Haslea karadagensis, and Haslea provincialis - in scientific papers.
Before the BIOVADIA project, Haslea's distribution and ecology around the world was relatively unknown. After scientists conducted many sampling campaigns across the globe during the project, they discovered Haslea. provincialis in the Mediterranean Sea, Haslea. silbo sp. nov. and Haslea acoran sp. nov in the Canary Islands and Haslea sp. in the Java Sea near Indonesia. "Thriving in a broad range of marine and climatic conditions across the globe, some of these species are tolerant and adaptable, making them potentially robust strains for mass production," says Perkins.
"The specificity of the blue Haslea inside the genus Haslea forms a very well-defined clade - group of organisms/species evolved from a common ancestor," explains Mouget. Scientifically, this is important because elements of the marennine-like pigment biosynthesis pathway should be present in other Haslea species, as well as in genetically related organisms (pennate diatoms, stramenopiles), even if they do not produce these specific pigments.
Exchange programmes - backing blue biotech
In addition to investigating the biodiversity of Haslea, the joint exchange programme investigated photobiology and genetic questions about Haslea. "The BIOVADIA research conducted the first genome sequencing of Haslea strains and started to understand how Haslea acclimatises to its light environment," says Perkins. When scientists understand how Haslea reproduces and which conditions help it to thrive, they could then start preparing to scale up the production of the marennine for biotechnological use.
"New collaborations have been developed during, and thanks to the BIOVADIA project," reports Mouget. Most partners involved in the BIOVADIA project are still working on blue Haslea, and are partners of a new four-year H2020 Research and Innovation Staff Exchange project called GHaNA that is investigating the Haslea genus.
In what is set to be a decade-long working relationship, Mouget and Perkins continue to build on the BIOVADIA research findings in the GHaNA project, which is scheduled for completion in 2021. Involving 22 partners in Europe, Canada, USA, Australia, Indonesia, Vietnam and Algeria, GHaNA will enable 356 research exchanges. "EU funding to cover research costs is an important facilitator for this type of collaboration project," points out Mouget.