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oai:uvadoc.uva.es:10324/787992025-10-20T19:01:36Zcom_10324_35294com_10324_952com_10324_894col_10324_35295

Digestate dilution shapes carbohydrate and pigment production during microalgal and cyanobacterial-based biogas upgrading Ciani, Matilde Vargas Estrada, Laura Gabriela Adessi, Alessandra Muñoz Torre, Raúl Biogas upgrading Metabolites Microalgae Nutrient recovery Wastewater dilution 3308 Ingeniería y Tecnología del Medio Ambiente Producción Científica Microalgae and cyanobacteria offer a promising platform for integrating sustainable technologies aligned with circular and green economy goals. However, current studies often focus on a limited number of genera and overlook how centrate dilution influences metabolite production. This study investigates the potential of the freshwater microalga Parachlorella hussii N9 and the marine cyanobacterium Cyanothece sp. CE4 for photobio- logical biogas upgrading coupled with nutrient recovery from centrate, assessing the impact of centrate dilution on carbohydrate and pigment content. By varying centrate concentration (5–50 %) in tap or seawater, this research explores how the biogas-to-centrate ratio can be adjusted for biomass production, TN and CO2 abate- ment, and to target specific metabolites, advancing circular bioeconomy strategies. The microalga exhibited faster growth than the cyanobacterium, achieving the stationary phase in three days, and higher cellular and soluble carbohydrate productivity (up to 237 and 75 mg L 1d 1, respectively). CO₂ abatement (almost complete in all treatments) reached ~513 ± 28 mg L 1 of culture, while nitrogen removal considering initial centrate concentration ranged between 32 and 250 mg N L 1, but 100 % TN removal was exhibited only with the lower centrate concentrations (5–10 %). These lower concentrations also induced the highest carbohydrate content in biomass (41–44 % dw). In contrast, pigment content increased with higher centrate concentrations: the micro- alga reached 3.6 % dw of chlorophyll at 50 % centrate, while the cyanobacterium produced up to 0.6 % dw of C- phycocyanin; both strains showed similar carotenoid content (0.4–0.5 % dw). This study highlights the potential of adjusting centrate dilution to target microalgal metabolism for integrated CO₂ capture, nutrient recovery, and bioproduct generation. This research was partially funded by the Department of Agriculture, Food, Environment and Forestry (DAGRI), University of Florence (call Finanziamento di Azioni di Internazionalizzazione - FAI 2024). 2025-10-20T08:37:51Z 2025-10-20T08:37:51Z 2025 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Algal Research, 2025, vol. 91, p. 104290 2211-9264 https://uvadoc.uva.es/handle/10324/78799 10.1016/j.algal.2025.104290 104290 Algal Research 91 eng https://www.sciencedirect.com/science/article/pii/S2211926425004011 Atribución-NoComercial 4.0 Internacional info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by-nc/4.0/ © 2025 The Author(s) application/pdf Elsevier https://uvadoc.uva.es/bitstream/10324/78799/4/Digestate-dilution-shapes-carbohydrate.pdf.jpg Hispana TEXT http://creativecommons.org/licenses/by-nc/4.0/ UVaDOC. Repositorio Documental de la Universidad de Valladolid https://uvadoc.uva.es/handle/10324/78799