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Biogas valorization via continuous polyhydroxybutyrate production by Methylocystis hirsuta in a bubble column bioreactor Rodríguez Muñoz, Yadira Firmino, Paulo Igor Milen Pérez, Víctor Lebrero Fernández, Raquel Muñoz Torre, Raúl Bioplásticos Biorrefinería Bioplastics Biorefinery 23 Química 33 Ciencias Tecnológicas Producción Científica Creating additional value out of biogas during waste treatment has become a priority in past years. Biogas bioconversion into valuable bioproducts such as biopolymers has emerged as a promising strategy. This work assessed the operational feasibility of a bubble column bioreactor (BCB) implemented with gas recirculation and inoculated with a polyhydroxybutyrate (PHB)-producing strain using biogas as substrate. The BCB was initially operated at empty bed residence times (EBRTs) ranging from 30 to 120 min and gas recirculation ratios (R) from 0 to 30 to assess the gas-to-liquid mass transfer and bioconversion of CH4. Subsequently, the BCB was continuously operated at a R of 30 and an EBRT of 60 min under excess of nitrogen and nitrogen feast-famine cycles of 24 h:24 h to trigger PHB synthesis. Gas recirculation played a major role in CH4 gas–liquid transfer, providing almost fourfold higher CH4 elimination capacities (~41 g CH4 m−3 h−1) at the highest R and EBRT of 60 min. The long-term operation under N excess conditions entailed nitrite accumulation (induced by O2 limiting conditions) and concurrent methanotrophic activity inhibition above ~60 mg N-NO2− L−1. Adjusting the N-NO3− supply to match microbial N demand successfully prevented nitrite accumulation. Finally, the N feast-famine 24 h:24 h strategy supported a stable CH4 conversion with a removal efficiency of 70% along with a continuous PHB production, which yielded PHB accumulations of 14.5 ± 2.9% (mg PHB mg−1 total suspended solids × 100). These outcomes represent the first step towards the integration of biogas biorefineries into conventional anaerobic digestion plants. Ministerio de Ciencia e Innovación (grant BES-2016-077160) y (proyecto CTM2015-70442-R) Junta de Castilla y León y EU-FEDER (CLU 2017-09) , (UIC 526071) y (VA281P18) 2021-06-04T12:23:23Z 2021-06-04T12:23:23Z 2020 info:eu-repo/semantics/article info:eu-repo/semantics/acceptedVersion Waste Management, 2020, vol. 113, p. 395-403 0956-053X https://uvadoc.uva.es/handle/10324/46752 10.1016/j.wasman.2020.06.009 395 403 Waste Management 113 eng https://www.sciencedirect.com/science/article/abs/pii/S0956053X20303196 Attribution-NonCommercial-NoDerivatives 4.0 Internacional info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by-nc-nd/4.0/ © 2020 Elsevier application/pdf Elsevier https://uvadoc.uva.es/bitstream/10324/46752/4/Biogas-valorization-via-continuous.pdf.jpg Hispana TEXT http://creativecommons.org/licenses/by-nc-nd/4.0/ UVaDOC. Repositorio Documental de la Universidad de Valladolid https://uvadoc.uva.es/handle/10324/46752