Rumen fermentation (RF) is a complex system of oxidation–reduction reactions governed by the rumen microbiota, and its end-products are the volatile fatty acids (VFAs) which constitute the main energy source for the host animal. We speculated that the process could be manipulated through electrofermentation (EF) by utilizing solid-state electrodes as electron sources. This study aimed to evaluate the effects of single-chamber EF applied (0.4 vs. 0.9 V) for 6, 12, or 24 h to rumen fluid on the resulting microbial biomass, dry matter digestibility (DMD), VFA production, NADH/NAD ratio, and composition of the rumen fluid’s bacterial communities. The application of a 0.9 V electric potential for 24 h produced the most significant changes in RF compared to the control treatment (0V), increasing microbial biomass (12%), DMD (58%), and VFA concentrations (~84%), and reducing NAD/NADH ratio (~50%) without a significant impact on bacterial diversity. These results suggest that the application of a 0.9 V electric potential allows the microbiota to better hydrolyze and digest the feed’s components and could offer an electron sink for the production of VFAs. Hence, EF can provide innovative solutions to a range of challenges that limit the RF process. Nonetheless, more studies are needed to understand how the solid electrodes and external electric energy function.

La fermentación ruminal (FR) es un proceso anaerobio de óxido-reducción realizado por una comunidad microbiana compleja, mediante el cual se generan ácidos grasos volátiles (AGV), principal fuente de energía para los rumiantes. Sin embargo, la FR también produce metano, un gas de efecto invernadero que afecta la sostenibilidad de los sistemas ganaderos. Esto ha impulsado el interés en estrategias que aumenten la eficiencia energética del rumen, lo que favorece una mayor producción de AGV y reduce simultáneamente las emisiones de metano por unidad de alimento fermentado. La electrofermentación (EF) puede considerarse como una alternativa innovadora para abordar estas limitaciones. Este enfoque combina fermentación microbiana con la aplicación de corrientes eléctricas mediante electrodos que funcionan como sumideros o fuentes de electrones. Al modificar el balance redox microbiano y superar restricciones termodinámicas, la EF redirige el flujo de electrones hacia rutas metabólicas que incrementan la síntesis de AGV. Estudios in vitro han demostrado aumentos superiores al 80% en la producción de AGV, acompañados de una reducción significativa del biogás y un incremento en biomasa microbiana. En conjunto, estos avances posicionan a la EF como una estrategia prometedora para mejorar la eficiencia alimentaria y disminuir el impacto ambiental de la ganadería, aunque su implementación in vivo requiere mayor investigación técnica y metodológica. https://doi.org/10.21929/abanicomicrobiano/2025.7 2025-7 https://www.youtube.com/watch?v=cAZisEK0sF8 Rumen fermentation (RF) is an anaerobic redox process carried out by a complex microbial community that generates volatile fatty acids (VFAs), the primary energy source for ruminants. However, RF also produces methane, a greenhouse gas that negatively impacts the sustainability of livestock systems. This has intensified interest in strategies aimed at improving rumen energy efficiency by increasing VFA production while simultaneously reducing methane emissions per unit of fermented feed. Electrofermentation (EF) has emerged as an innovative alternative to address these limitations. This approach integrates microbial fermentation with the application of electrical currents through electrodes that act as electron sinks or sources. By modifying the microbial redox balance and overcoming thermodynamic constraints, EF redirects electron flow toward metabolic pathways that enhance VFA synthesis. In vitro studies have reported increases of over 80% in VFA production, accompanied by significant reductions in biogas generation and increased microbial biomass. Collectively, these findings position EF as a promising strategy to improve feed efficiency and reduce the environmental impact of livestock production, although its in vivo implementation still requires further technical and methodological research. https://doi.org/10.21929/abanicomicrobiano/2025.7 2025-7 https://www.youtube.com/watch?v=cAZisEK0sF8