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Producción Científica, This study aimed at investigating the feasibility of using a highly specialized bacterial inoculum harboring lactic acid bacteria (LAB) and lactate-oxidizing, hydrogen-producing bacteria (LO-HPB) to produce either lactate or biohydrogen and butyrate from several agro-industrial resources via dual-phase dark fermentation. The feedstocks were fruit–vegetable waste, cheese whey, coffee wastewater, tequila vinasse, and maize processing wastewater, and were tested in both mono- and co-fermentation. The results obtained indicated that the biocatalyst used was able to perform a dual-phase lactate fermentation, producing high lactate (13.1–36.4 g/L), biohydrogen (0.2–7.5 NL H2/Lfeedstock, equivalent to 0.3–1.7 mol H2/mol hexose), and butyrate (3.3–13.9 g/L) with all the tested feedstocks. A series of self-fermentation tests were also performed with crude cheese whey and fruit–vegetable waste for comparison purposes. Compared to inoculum-aided fermentations, the self-fermentation exhibited a reduced bioconversion efficiency. Short-length 16S rRNA gene sequencing analysis showed that LO-HPB was the dominant microbial group (86.0%) in the biocatalyst, followed by acetic acid bacteria (5.8%) and LAB (5.7%). As expected, the molecular analysis also showed significant differences in the microbial community structure of the biocatalyst and those that evolved from self-fermentation. Besides lactate fermentation and oxidation, the biocatalyst also assisted the bi-phasic lactate fermentation via oxygen consumption, and apparently, via substrate hydrolysis. Overall, this study can lay the foundation for robust inoculum development, which is of special significance in the field of dark fermentation, and proposes an innovative bioprocess for agro-industrial valorization through a trade-off approach, tailoring the metabolic pathway to the target product(s)., Consejo Nacional de Humanidades, Ciencias y Tecnologías (CONAHCYT) - (Project-PN-2015-01-1024), Ministerio de Ciencia e Innovación/Agencia Estatal de Investigación (AEI)/10.13039/501100011033 y Unión Europea NextGenerationEU/PRTR - (grant RYC2021-034559-I), Junta de Castilla y León y Fondo Europeo de Desarrollo Regional (FEDER) - (grant CL-EI-2021-07 y UIC 315)

Producción Científica, The present study investigated the physicochemical and microbiological changes occurring during the storage of simulated restaurant food waste (FW) and how such changes affected its biohydrogen and biogas production potential. FW was stored for 72 h in a closed atmosphere under two different scenarios: i) without and ii) with inoculation of a mixed microbial culture harboring lactic acid bacteria (LAB). Both storage scenarios resulted in similar biotic and abiotic changes in FW. Particularly, FW was pre-acidified and pre-hydrolyzed to some extent during the storage, resulting in a feedstock enriched in LAB (≈ 95 % total relative abundance) and lactate (10.5–12.3 g/L, 87.0–90.5 % selectivity). Biochemical hydrogen potential tests revealed that the use of stored FW resulted in similar or even higher hydrogen production efficiencies compared to that of non-stored FW, achieving up to 60 NmL H2/g VS added and a maximum volumetric hydrogen production rate of 9.7 NL H2/L-d. Metabolically, the conversion of lactate into hydrogen was crucial regardless of the use of non-stored or stored FW, albeit the presence of fermentable carbohydrates in the substrate was also essential either to produce lactate or to co-produce extra hydrogen. On the contrary, biochemical methane potential tests showed that the biogas production potential of FW was not affected by storage, yielding on average 400 NmL CH4/g VS added and revealing that lactate oxidation to methane precursors represented an important step in FW biomethanization., European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 894515, Ministerio de Ciencia e Innovación - AEI and European Union NextGenerationEU/PRTR (RYC2021-034559-I), Junta de Castilla y León and the European FEDER Programme (CLU 2017-09, CL-EI-2021-07 y UIC 315)

El biohidrógeno es una fuente de energía renovable prometedora, pudiendo ser producido biológicamente a partir de diversas residuos orgánicos y aguas residuales vía fermentación oscura, que constituye un proceso atractivo debido a sus altas productividades y operación simple. En este estudio, se investigaron diferentes estrategias de operación con el objetivo de optimizar la producción de hidrógeno (H2) mediante fermentación oscura, utilizando lactosuero en polvo como sustrato, con enfoque en la vía metabólica del lactato. Experimentos en lote fueron llevados a cabo para conocer la producción de H2 (2004,5 ± 84,7 NmL H2/Lreactor) y consumo de sustrato (94,48 ± 0,87 %) en el sistema e inferir sobre las principales vías de generación de hidrógeno por análisis de ácidos orgánicos. La operación en continuo fue realizada en cinco fases: fase control (I), adición de medio soporte inerte (II), introducción de nanopartículas de hierro encapsuladas en carbono (100 ppm) (III) y nanopartículas de Fe2O3 a concentración 100 ppm (IV) y 300 ppm (V). En configuración en lote, se observó que las principales vías de producción de H2 estuvieron principalmente relacionadas a las vías del acetato y lactato, con aproximadamente 75,65 % de la productividad siendo explicada por estas vías metabólicas. La utilización de medio soporte fue fundamental para la estabilización del sistema en continuo, cuya máxima productividad (27276 NmL/L-d) fue alcanzada en presencia de nanopartículas de Fe2O3 (300 mg/L). La producción adicional de H2 en el sistema en continuo posiblemente se debió a la activación o mejoramiento de la ruta metabólica del lactato, a partir de la utilización de metabolitos intermediarios, sin ocasionar alteración en el consumo de sustrato o en la concentración de biomasa. La utilización de nanotecnología se ve una alternativa prometedora para el incremento de la productividad de biohidrógeno impulsada por la ruta metabólica del lactato., Biohydrogen is a promising renewable energy source that can be produced from a wide variety of organic substrates and wastewaters via dark fermentation, which represents an attractive process due to its relative high productivity and simple operation. In this study, different operational strategies were investigated with the aim of optimizing hydrogen (H2) production through dark fermentation, using cheese whey powder as substrate, with a focus on the lactate-utilizing, hydrogen-producing pathway. Batch experiments were carried out to determine the H2 production (2004.5 ± 84.7 NmL H2/Lreactor) and substrate consumption (94.48 ± 0.87%) profiles in the system and infer about the main H2 production pathways by analysis of organic acids. Continuous operation was carried out in five stages: control (I), addition of inert support medium (II), introduction of iron nanoparticles encapsulated in carbon (100 ppm) (III) and Fe2O3 at a concentration of 100 ppm (IV) and 300 ppm (V). Under batch operation, the main H2 production pathways were mainly related to the acetate and lactate pathways, with approximately 75.65% of the productivity being explained by these metabolic routes. The use of support medium was fundamental for the stabilization of the continuous system, whose maximum productivity (27276 NmL/L-d) was reached in the presence of Fe2O3 nanoparticles (300 mg/L). The additional production of H2 in the continuous system was likely possibly due to the activation or improvement of the lactate metabolic pathway, from the use of intermediate metabolites, without causing alterations in the consumption of substrate or in the concentration of biomass. The use of nanotechnology is a promising alternative for increasing biohydrogen productivity driven by the lactate metabolic pathway, Departamento de Ingeniería Química y Tecnología del Medio Ambiente, Máster en Ingeniería Ambiental

El elevado número de campamentos que se desarrollan en la actualidad suponen un gran impacto ambiental en zonas naturales ya que no disponen de una infraestructura adecuada para la gestión de aguas residuales. En este Trabajo de Fin de Grado se han estudiado de forma teórica las diferentes opciones que existen actualmente para la gestión de aguas residuales y que se podrían utilizar en los campamentos de verano, para finalmente, seleccionar la mejor opción para construir una planta piloto portátil del proceso de tratamiento de aguas residuales fecales generadas en campamentos de verano cuyo objetivo es minimizar el impacto ambiental de esta actividad recreativa. El proceso de depuración que se propone se basa en una digestión anaerobia de heces y orines a temperatura ambiente, acoplada a una separación sólido-líquido por sedimentación seguida de una etapa de biofiltración aerobia y de una etapa de desinfección solar con el objetivo de eliminar la totalidad de la materia orgánica, patógenos y nitrógeno amoniacal de las aguas residuales fecales. Se trata de un proceso sostenible y de bajo consumo energético, basado en la acción biocatalítica de microorganismos, en la sedimentación por gravedad y en el potencial de desinfección de luz solar. En el proceso también se produciría biogás que por su alto poder calorífico podría emplearse como combustible para cocinar en los campamentos., The high number of camps that are currently being developed have a great environmental impact on natural areas because they do not have adequate infrastructure for wastewater management. In this Final Degree Project we have studied theoretically the different options that currently exist for wastewater management and that could be used in summer camps, to finally select the best option to build a portable pilot plant for the treatment process of fecal wastewater generated in summer camps with the objective of minimizing the environmental impact of this recreational activity. The proposed purification process is based on an anaerobic digestion of feces and urine at ambient temperature, coupled with a solid-liquid separation by sedimentation followed by an aerobic biofiltration stage and a solar disinfection stage with the objective of eliminating all organic matter, pathogens and ammonia nitrogen from the fecal wastewater. This is a sustainable process with low energy consumption, based on the biocatalytic action of microorganisms, gravity sedimentation and the disinfection potential 3 of sunlight. The process would also produce biogas which, due to its high calorific value, could be used as fuel for cooking in the camps., Departamento de Ingeniería Química y Tecnología del Medio Ambiente, Grado en Ingeniería Química

Producción Científica, The feasibility of producing volatile fatty acids (VFAs) from five commercial bioplastics via acidogenic fermentation by a non-pretreated anaerobic sludge was investigated. Mesophilic, anaerobic, acidogenic batch assays at 1, 10 and 20 g/L feed concentrations revealed the feasibility of producing VFAs from polyhydroxyalkanoates (PHA), i.e., PHB and PHBV, but not from PBS, PCL and PLA under the test conditions and time. However, only high PHA substrate concentrations (10–20 g/L) resulted in organic overloading and decreasing the pH of the culture broth down to 4–5, which in turn induced the accumulation of VFAs via kinetic imbalance between acidogenesis and methanogenesis. Gaseous carbon (C-CO2 and C-CH4) accounted for 8–35% of the total initial carbon, while C-VFAs represented 10–18%, mainly as acetate and butyrate. This study represents the first systematically assessed proof-of-concept to produce VFAs from PHA, which is key for the design of bioplastic-to-bioplastic recycling (bio)technologies., Junta de Castilla y Leon - Fondo Europeo de Desarrollo Regional (grants CLU 2017-09, CL-EI-2021-07 and UIC 315)

Producción Científica, This study proposed a lactate-based two-stage anaerobic digestion (AD) process to enhance bioenergy production rate from food waste (FW) and investigated the effect of inoculum addition and culture pH on hydrolysis-acidogenesis and further methanization. A series of batch fermentations were performed with an enriched lactate-producing consortium and without inoculum addition under controlled (5.7) and uncontrolled pH (initial 6.7) conditions. The interplay between the studied factors dictated the fate of lactate, particularly if it is produced and accumulated in the fermentation broth or is consumed by butyrogenic bacteria. Only the self-fermentation of FW with uncontrolled pH resulted in lactate accumulation (0.2 g/g volatile solid (VS) fed) with limited off-gas production (0.32 NL/L) and VS losses (≈16%). Such lactate-rich broth was successfully digested through biochemical methane potential tests, resulting in a maximum bioenergy production rate of 2891 MJ/ton-VS fed per day, which was two-fold higher compared to that achieved by one-stage AD., Junta de Castilla y León - Fondo Europeo de Desarrollo Regional (projects CLU 2017-09 and UIC 315)