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bioRxiv · 10.1101/2025.05.22.655468

Elevated carbon dioxide stimulates highly efficient organic-carbon consumption and confectionary-waste valorization under mixotrophy in the unicellular alga Galdieria

Masson, M. L. P.·de Freitas, B. B.·Zybinskii, A.·Althagafi, G.·Amad, M.·Fox, M. D.·Lammers, P. J.·Lauersen, K. J.
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Abstract

Unicellular algae are appealing for nutritional and biotechnological utility but have wide variation across strains and can be challenging to produce. The thermo-acidophilic algal genus Galdieria use diverse organic-carbon sources for fermentative growth that can include waste-stream feedstocks and have complete amino-acid compositions for human nutrition. Here, we investigated Galdieria metabolic dynamics to catalog organic-carbon conversion to biomass. Tested strains had enhanced growth upon 3% CO2 supplementation, triggering efficient glucose uptake to reach [~]5 {+/-} 0.3 g dry biomass L-{superscript 1}. Stable-isotope analysis revealed that organic-carbon uptake dominates CO2 fixation in darkness under mixotrophy, with CO2 an apparent metabolic trigger. Galdieria sulphuraria 5587.1 can consume up to 8.3 g carbon L-1 day-1 from industrial confectionery waste, with C-phycocyanin reaching 3.8% of dry biomass and remaining thermostable at 72{degrees}C. This framework can optimize Galdieria-based bioprocesses for inexpensive waste conversion into high-value biomass and identifies CO2 as a trigger of organic-carbon assimilation, even in heterotrophic conditions. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=135 SRC="FIGDIR/small/655468v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@e2ef63org.highwire.dtl.DTLVardef@d28574org.highwire.dtl.DTLVardef@137be97org.highwire.dtl.DTLVardef@c1c0a5_HPS_FORMAT_FIGEXP M_FIG C_FIG

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Masson, M. L. P., de Freitas, B. B., Zybinskii, A., Althagafi, G., Amad, M., Fox, M. D., Lammers, P. J., Lauersen, K. J.. 2025-05-27. Elevated carbon dioxide stimulates highly efficient organic-carbon consumption and confectionary-waste valorization under mixotrophy in the unicellular alga Galdieria. https://doi.org/10.1101/2025.05.22.655468

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