Natural pigments and biogas recovery from cyanobacteria grown in treated wastewater. Fate of organic microcontaminants | Recuperación de pigmentos naturales y biogás a partir de cianobacterias cultivadas en aguas residuales tratadas. Destino de los microcontaminantes orgánicos

Cyanobacterial wastewater-based biorefineries are a sustainable alternative to obtain high-value products with reduced costs. This study aimed to obtain phycobiliproteins and carotenoids, along with biogas from a wastewater-borne cyanobacterium grown in secondary effluent from an urban wastewater treatment plant, namely treated wastewater. For the first time, the presence of contaminants of emerging concern in concentrated pigment extracts was assessed. Tertiary wastewater treatment was conducted in a 3 L photobioreactor inoculated with Synechococcus sp., and operated in semi-continuous regime with a hydraulic retention time of 6 days. The carotenoid content was stable (reaching up to 4 mg g DW-1) regardless of the wastewater composition, while the phycobiliprotein content (up to 214 mg g DW-1) varied according to nitrogen availability. In concentrated pigment extracts, only 3 (out of 20) organic microcontaminants were detected. The biochemical methane po tential of pigment-extracted biomass (222 NL CH4 kg VS- 1 ) was still 72 % of raw biomass. In conclusion, a cyanobacteria culture rich in Synechococcus sp. appears as a promising source of bio-based products in a circular economy approach.

This research was funded by the R + D + I projects AL4BIO (RTI2018-099495-B-C21) and Cyan2Bio (PID2021-126564OB-C32), funded by MCIN/AEI/ 10.13039/501100011033 and “ERDF A way of making Europe’’. Marta Bellver acknowledges her grant PRE2019-091552 funded by MCIN/AEI/ 10.13039/501100011033 and by “ESF Investing in your future”. Evelyn Ruales acknowledges her grant 2020 FISDUR 00592 from AGAUR Agència de Gestió d'Ajuts Universitaris i de Recerca. Monica Escolà is grateful to the Beatriu de Pinós 2018 grant-programme (MSCA grant agreement number 801370).

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