Impact on the microbial population during biological volatile fatty acid production from olive mill solid waste Jiménez Páez, Elena Serrano Moral, Antonio Purswani, Jessica Renuka Mohan Correa Galeote, David Anaerobic digestion Operational pH Propionic acid Lignocellulosic material Phenolic compounds This work was funded by the Spanish Ministry of Economy, Industry and Competitiveness (Ref. PID2020-116698RB-100). Dr. Antonio Serrano was funded by the Consejería de Transformación Económica, Industria, Conocimiento y Universidades (Junta de Andalucía - EMERGIA20_00114). Juan Cubero-Cardoso was funded by the Recualificación del Profesorado Universitario (Next Generation European Funds and Spanish University Ministry system). Supplementary material: Download Word document (34KB), 1-s2.0-S2352186423004054-mmc1 Volatile fatty acids (VFAs) revalorisation from waste products are key in achieving industrial sustainability and circular economic goals. Hence, the objective of this work was to correlate the adaptability of the microbial community in olive mill solid waste (OMSW) anaerobic fermentation processes, to the production of VFAs under different pH conditions, i.e. under acidic (pH 4 &5), neutral (pH 6 & 7) and alkaline conditions (pH 9 & 10). At neutral conditions, anaerobic digestion exhibited minimal accumulation of VFAs, as they were primarily biotransformed to methane, where no significant changes in the microbial community were observed. At acidic conditions, a diverse profile of VFAs were present in the reactors, although the VFA production was limited to around 20 % of fed OMSW. Despite the low accumulation, the VFA profile at pH 5 was more complex than those at alkaline conditions, accounting propionic acid as the main VFA compound produced at pH 5 (60 % of the total VFAs). Acidic conditions entailed a shift in the microbial composition compared to the initial inoculum, although the reactors maintained similar diversity indices. At alkaline conditions, around 50 % of the fed OMSW was accumulated as VFAs, mainly as acetic acid. Overall, a lower diversity and higher dominance corresponded to a less diverse VFAs profile, such as the preponderance of acetic acid correlated with a microbial diversity decrease and the increased dominance of Tissirella. 2023-12-05T12:07:45Z 2023-12-05T12:07:45Z 2023-11 info:eu-repo/semantics/article E. Jiménez-Páez et al. Impact on the microbial population during biological volatile fatty acid production from olive mill solid waste. Environmental Technology & Innovation 32 (2023) 103409. [https://doi.org/10.1016/j.eti.2023.103409] https://hdl.handle.net/10481/86039 10.1016/j.eti.2023.103409 eng http://creativecommons.org/licenses/by/4.0/ info:eu-repo/semantics/openAccess Atribución 4.0 Internacional Elsevier