Producción de biohidrógeno sustentable a partir de residuos orgánicos: Estudio de la fermentación oscura del mucílago de café bajo diferentes estrategias operacionales
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Date
2026
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Publisher
Universidad de Concepción
Abstract
La transición energética hacia la neutralidad de carbono posiciona al hidrógeno como un vector estratégico, lo que exige que su producción migre desde rutas basadas en combustibles fósiles hacia alternativas renovables. Entre ellas, la fermentación oscura en cultivos mixtos ofrece una alternativa atractiva al valorizar residuos orgánicos y promover la economía circular; sin embargo, su estabilidad se ve comprometida por la dinámica microbiana, especialmente en residuos ricos en carbohidratos donde proliferan bacterias ácido lácticas. Aunque el ácido láctico se ha descrito tradicionalmente como un inhibidor de bacterias productoras de hidrógeno (BPH), evidencia reciente indica que, bajo limitación de carbohidratos, este metabolito puede actuar como sustrato para BPH y contribuir a la estabilidad del proceso al disminuir la competencia microbiana. En esta investigación se evaluó la producción de biohidrógeno mediante fermentación oscura usando mucílago de café (Coffea arabica) acidificado naturalmente como sustrato enriquecido en ácido láctico, analizando el efecto combinado del tiempo de retención hidráulica (TRH: 0,5-3,5 días) y la concentración de ácido láctico en la alimentación (CAL: 5-35 g/L) sobre el desempeño operativo, la cinética y la comunidad microbiana en un biorreactor semicontinuo operado bajo condiciones mesofílicas (31,0 ± 1,0 °C) y pH 6,7. Los resultados indican que combinaciones de TRH ≤ 1 día y CAL de 10 - 20 g/L favorecieron la producción de hidrógeno y ácido butírico, con baja acumulación de ácido propiónico, consistente con el predominio de rutas fermentativas butíricas. El ajuste cinético con el modelo de Gompertz modificado evidenció coincidencia temporal entre el máximo consumo de ácido láctico y la máxima actividad hidrogenogénica. Desde la perspectiva microbiológica, el régimen operativo actuó como una presión de selección, favoreciendo la persistencia de un núcleo funcional resiliente. Se identificaron géneros clave como Lysinibacillus, Bacillus y Enterobacter, cuya presencia se asoció a las altas tasas de producción de hidrógeno a TRH de 0,5 días y CAL de 20 g/L. En conclusión, el acoplamiento estratégico de TRH y CAL es crítico para la estabilidad y configuración funcional del consorcio microbiano durante la fermentación oscura semicontinua impulsada por lactato. Finalmente, el mucílago de café acidificado demostró ser un sustrato viable y representativo, lo que abre posibilidades para extrapolar estos principios hacia otros residuos agroindustriales ricos en ácido láctico, consolidando esta ruta como alternativa biotecnológica robusta para la producción de energía limpia.
The energy transition toward carbon-neutral system defines hydrogen as a strategic energy vector, which requires its production to shift from fossil fuel-based routes to renewable alternatives. Among them, dark fermentation in mixed cultures offers an attractive option by valorizing organic residues and promoting a circular economy; however, process stability depends upon microbial dynamics, particularly carbohydrate-rich waste with the proliferation of lactic acid bacteria. Although lactic acid has traditionally been described as inhibitor of hydrogen-producing bacteria (HPB), recent evidence indicates that at carbohydrate limitations this metabolite can act as substrate for HPB and contributes to process stability by reducing microbial competition. In this research, biohydrogen production via dark fermentation was evaluated using naturally acidified coffee mucilage (Coffea arabica) as a lactic acid-enriched substrate, analyzing the combined effect of hydraulic retention time (HRT: 0.5-3.5 days) and lactic acid concentration in the feed (CLA: 5-35 g/L) on operational performance, kinetics, and microbial community in a semi-continuous bioreactor operated at mesophilic conditions (31.0 ± 1.0 °C) and pH 6.7. The results indicate that HRT ≤ 1 day and CLA of 10-20 g/L favored hydrogen and butyric acid production, with low propionic acid accumulation, consistent with the predominance of butyrate-type fermentation pathways. Kinetic fitting according to the modified Gompertz model revealed temporal coincidence between maximum lactic acid consumption and maximum hydrogenogenic activity. From a microbial point of view, the operating regime acted as a selective pressure, promoting the persistence of a resilient functional core. Key genera such as Lysinibacillus, Bacillus and Enterobacter were identified, whose presence was associated with high hydrogen production rates and HRT of 0.5 days and CLA of 20 g/L. In conclusion, the strategic coupling of HRT and CAL is critical for stability and functional configuration of the microbial consortium during lactate driven semi-continuous dark fermentation. Finally, naturally acidified coffee mucilage proved to be a viable and representative substrate, offering opportunities to extrapolate these principles to other lactic acid-rich agro-industrial waste, thereby consolidating this route as a robust biotechnological alternative for clean energy production.
The energy transition toward carbon-neutral system defines hydrogen as a strategic energy vector, which requires its production to shift from fossil fuel-based routes to renewable alternatives. Among them, dark fermentation in mixed cultures offers an attractive option by valorizing organic residues and promoting a circular economy; however, process stability depends upon microbial dynamics, particularly carbohydrate-rich waste with the proliferation of lactic acid bacteria. Although lactic acid has traditionally been described as inhibitor of hydrogen-producing bacteria (HPB), recent evidence indicates that at carbohydrate limitations this metabolite can act as substrate for HPB and contributes to process stability by reducing microbial competition. In this research, biohydrogen production via dark fermentation was evaluated using naturally acidified coffee mucilage (Coffea arabica) as a lactic acid-enriched substrate, analyzing the combined effect of hydraulic retention time (HRT: 0.5-3.5 days) and lactic acid concentration in the feed (CLA: 5-35 g/L) on operational performance, kinetics, and microbial community in a semi-continuous bioreactor operated at mesophilic conditions (31.0 ± 1.0 °C) and pH 6.7. The results indicate that HRT ≤ 1 day and CLA of 10-20 g/L favored hydrogen and butyric acid production, with low propionic acid accumulation, consistent with the predominance of butyrate-type fermentation pathways. Kinetic fitting according to the modified Gompertz model revealed temporal coincidence between maximum lactic acid consumption and maximum hydrogenogenic activity. From a microbial point of view, the operating regime acted as a selective pressure, promoting the persistence of a resilient functional core. Key genera such as Lysinibacillus, Bacillus and Enterobacter were identified, whose presence was associated with high hydrogen production rates and HRT of 0.5 days and CLA of 20 g/L. In conclusion, the strategic coupling of HRT and CAL is critical for stability and functional configuration of the microbial consortium during lactate driven semi-continuous dark fermentation. Finally, naturally acidified coffee mucilage proved to be a viable and representative substrate, offering opportunities to extrapolate these principles to other lactic acid-rich agro-industrial waste, thereby consolidating this route as a robust biotechnological alternative for clean energy production.
Description
Tesis presentada para optar al grado de Doctora en Recursos Hídricos y Energía para la Agricultura
Keywords
Hidrógeno, Residuos orgánicos como combustible, Economía circular