Report
Teaser, summary, work performed and final results
Periodic Reporting for period 1 - GHaNA (The Genus Haslea, New marine resources for blue biotechnology and Aquaculture)
Teaser
The GHaNA project aims to explore and characterize a new marine bioresource the genus Haslea for blue biotechnology applications in aquaculture, cosmetics and possibly food and health industry. Biological and chemical diversity of Haslea diatoms will be determined using...
Summary
The GHaNA project aims to explore and characterize a new marine bioresource the genus Haslea for blue biotechnology applications in aquaculture, cosmetics and possibly food and health industry. Biological and chemical diversity of Haslea diatoms will be determined using biological, physiological and genomic approaches. In the long run, mass-scale production will be developed for viable industrial applications by maximising biomass production and associated high-value compound production.
Besides the increase of our functional knowledge about this original bioresource, the benefits of this project should concern the industrial exploitation of dyes and bioactive compounds through commercial activities in the aquaculture, agri-food, cosmetics and health sectors, potentially offering valuable alternative to synthetic blue colorant or even to antibiotics.
Work performed
Until the last decade, have been included in the genus Haslea all diatoms with longitudinal striae of the valve external surface. The type species of the genus is Haslea ostrearia that produces a blue-green pigment, marennine, responsible for the greening of oysters (red label ‘fine de claire verte’). Regarding biodiversity, we focused on both blue- and non-blue Haslea species. Samples were practically collected from the whole world ocean and strains characterized. The use of molecular markers has shown that some of these newly established species belong to a group within the genus Navicula, a close relative of Haslea. We propose to call these diatoms Haslea-like species and to accommodate them in a new genus, we provisionally name Pseudo-haslea.
Substantial progress in marennine characterization has been made; according to last experimental data, we hypothesize that marennine is constituted by a glycosidic backbone to which a chromophore is linked. Work is in progress to understand the linkage between and the spatial disposition of the monosaccharides and to determine the nature of the chromophore.
Regarding photobiology, the work investigates photoadaptation capacities and photoacclimation strategies, comparing Haslea species and strains originating from different geographic areas, from the Arctic to the Equator. The first results have determined that Haslea diatoms rapidly, but transiently, upregulate electron transport following manipulation of light environment. This is of essential importance for blue biotechnology, for photobioreactor control of biomass yield and potentially marennine or high-value compounds production.
The chemical diversity of isoprenoids produced by different Haslea strains is currently investigated and the influence of environmental factors and geographic distribution in the chemical composition and production levels of highly branched isoprenoids (HBIs) is studied. Transcriptomic together with genomic information available was mined for the identification of H. ostrearia HBI-synthesizing enzyme candidates through a homology based approach using available sequenced diatom genomes and filtering of functional terms related to terpene synthesis. Candidate terpene synthase genes were analysed using a range of heterologous expression systems for the characterization of bioactivity.
On the aquaculture side, the greening of oysters by marennine increases their market value, and this represents the only example of exploitation of Haslea and marennine at the economic level, although marennine also displays valuable biological activities, antioxidant, antiproliferative, antibacterial. The possible impact of marennine was studied on a broad panel of marine microorganisms and invertebrates. Different species and strains of Vibrio exposed to environmentally relevant concentrations of marennine revealed usually sensitive, being inhibited, more rarely stimulated. Experiments were also conducted on embryos and/or larvae of different marine invertebrates, and different challenge tests with pathogen cultures or with infected hosts protected by marennine have been realized on Pacific oyster adults, blue mussel larvae and juvenile (spat), American oyster larvae. Protective effect of marennine has been demonstrated at low concentration, but high marennine concentration showed toxic effect on larvae or negative impact on physiology of adult oysters. These results presently limit the conditions of use of the marennine on larvae for shellfish aquaculture industry.
Final results
GHaNA main objectives are to determine the biological and chemical diversity of the genus Haslea, to develop mass-scale production processes, to achieve viable industrial production of biomass and associated high-value compounds, including terpenoids, blue pigments, lipids and silica skeletons. Haslea diatoms have a high potential for use in (1) existing oyster farming, (2) the production of pigments and bioactive compounds with natural antibacterial properties, and (3) novel applications as an industrial colouring agent, while (4) their silica skeleton wastes can be exploited as inorganic “biocharges†in the formulation of new elastomeric materials.
Two new projects were funded by the Région Pays de la Loire, one aims to study marennine redox behaviour in view of application as sensitive element in oxygen or pH sensors, and to work on the extraction and the characterization of the protein and carbohydrate fractions of Haslea biomass (collaboration with Univ. Laval, Canada), for which little is known, in comparison with the lipid fraction. The other aims to demonstrate the protective effect of marennine-like pigments against fish pathogens in aquaculture, and to promote their use at the industrial level in collaboration with the GHaNA partner at Stony Brook (USA).
A new method to extract marennine from the supernatant has been developed. It provides a very concentrated solution using a more simple and efficient protocol than previously in use, and a patent describing this new procedure has been filed. To exploit the patent, a funding has been obtained from the Société d’Accélération du Transfert de Technologies « Ouest Valorisation » (France) to work on the production of biomass and the chemical structure analyses.
New challenges have emerged since the start of GHaNA, mainly resulting from the worldwide observation of blue Haslea blooms in natural environments, and the fast development of omics and blue biotechnologies. A new project just started in Corsica (France) in collaboration with the Université de Liège (Belgium) to study the development of yearly blue Haslea blooms in the Bay of Calvi. The project also involves UNC to compare with the development of blue Haslea in the East coast of the USA, in order to understand the determinism of these blooms and the possible impacts on marine flora and fauna.
Last, a new research avenue opportunistically appeared in taxonomy and phylogeny. Based on the success of the sampling campaigns and the diversity of strains maintained in cultures, genomic comparisons are currently performed. Using information principally based on molecular markers and supported by electron microscopy, our team can distinguish between species belonging to Haslea (either blue or non-blue) and Haslea-like species, presently included into different genera of Naviculaceae. This allows redefining the morphological criteria for the genus Haslea, and proposing a new genus for Haslea-like species, we provisionally name Pseudo-haslea.
Website & more info
More info: http://ghana.univ-lemans.fr/en/index.html.