Erwan Le Gélébart1, Maëva Menguy1, Julien Fouilland1, Esther Causin1, Rémi Laville1
1 SEPPIC, Innovation Direction, Z.I.. – B.P. 72 – 22260 Pontrieux – France
Productivity intensification of microalgal biomasses has been studied for a few decades, heterotrophy or mixotrophy are serious options to promote specific metabolic pathways (1). To our knowledge there is no record of heterotrophic or mixotrophic cultivation of macroalgae. Our previous work showed that host-microbiota balance is a key factor to keep macroalgae in good conditions (2). We also demonstrated that it is possible to screen strains able to grow under mixotrophy with their microbiota (3). Two of these non-axenic macroalgae were selected to assess culture scale-up feasibility in the presence of organic carbon.
A green and a red macroalgae were grown under autotrophic and mixotrophic conditions in 300L airlift photobioreactors in a modified Provasoli medium under continuous light at 20°C for 14 days. Addition of organic carbon in the mixotrophic culture was the sole diverging condition from the autotrophic culture. Cultures were reproduced to assess process robustness.
Mixotrophy led to an increase of productivity of 50 to 70% depending on the tested strain and had an impact on suspensions morphology and their physical properties.
Water extracts of mixotrophic and autotrophic biomasses were analysed through High Pressure Liquid Chromatography (HPLC) coupled with a Diode Array Detector (DAD). Results showed their phytochemical content was notably different in terms of quality and quantity.
Underlying mechanisms managing microbiota-algae interaction in the presence of additional organic carbon sources are still to be investigated to optimize this new way of biomass production.
Scale-up feasibility, increase of productivity and phytochemical content differentiation makes this proof of concept a success to produce innovative cosmetic active ingredients.
(1) Liang, Yanna, Nicolas Sarkany, and Yi Cui. “Biomass and lipid productivities of Chlorella vulgaris under autotrophic, heterotrophic and mixotrophic growth conditions.” Biotechnology letters 31.7 (2009): 1043-1049.
(2) Le Gelebart, et al. Microbiota interactions with Laminariales gametophytes, impact on phytochemistry. Proceedings of the 23th International Seaweed Symposium 2019.
(3) Le Gelebart, et al. Investigating The Ability Of Laminariales Gametophytes For Organic Carbon Assimilation, Insights For Culture Intensification. Proceedings of the International Society for Applied Phycology 2020.