•The effects of NZVI (5–9 mg/gVS) on the AD of SS were studied.•High values of ETS activity (20.1–37.1 µgINTred/gVS·h) were reached with NZVI.•NZVI presented higher effects in early stages of AD and ...promoted the acetogenesis.•NZVI decreased the ORP to −300 mV and increased the VFA’s concentration.•The maximum methane yield (238 mLCH4/gVS) was achieved with 9 mg/gVS.
This work studied the effects on the anaerobic digestion of sewage sludge by zero valent iron nanoparticles (NZVI) dosage. Biochemical methane potential tests were carried out with 5–9 mg/gVS (99.7%, 40–60 nm). The biogas yield increased from 132 (control) to 310 mL/gVS with 9 mg/gVS. The methane content increased from 63.2% (control) to 77.6% with NZVI, which corresponded to a maximum yield of 238 mLCH4/gVS with 9 mg/gVS. The maximum VS reduction was 19.6%. The highest INT-ETS activity (20.1–37.1 µgINTred/gVS·h) corresponding to the maximum values of sCOD was reached within the first days. NZVI decreased the ORP to −300 mV and increased the VFA’s concentration (+2000 mg/L). The ORP-VFA-pH analysis showed that NZVI promoted the acidogenesis-acetogenesis without acidification. That is, NZVI was effective in intensifying the performance and stability of the process.
The purple non-sulfur bacterium Rhodopseudomonas palustris is recognized as a critical microorganism in the nitrogen and carbon cycle and one of the most common members in wastewater treatment ...communities. This bacterium is metabolically extremely versatile. It is capable of heterotrophic growth under aerobic and anaerobic conditions, but also able to grow photoautotrophically as well as mixotrophically. Therefore R. palustris can adapt to multiple environments and establish commensal relationships with other organisms, expressing various enzymes supporting degradation of amino acids, carbohydrates, nucleotides, and complex polymers. Moreover, R. palustris can degrade a wide range of pollutants under anaerobic conditions, e.g., aromatic compounds such as benzoate and caffeate, enabling it to thrive in chemically contaminated environments. However, many metabolic mechanisms employed by R. palustris to breakdown and assimilate different carbon and nitrogen sources under chemoheterotrophic or photoheterotrophic conditions remain unknown. Systems biology approaches, such as metabolic modeling, have been employed extensively to unravel complex mechanisms of metabolism. Previously, metabolic models have been reconstructed to study selected capabilities of R. palustris under limited experimental conditions. Here, we developed a comprehensive metabolic model (M-model) for R. palustris Bis A53 (iDT1294) consisting of 2,721 reactions, 2,123 metabolites, and comprising 1,294 genes. We validated the model using high-throughput phenotypic, physiological, and kinetic data, testing over 350 growth conditions. iDT1294 achieved a prediction accuracy of 90% for growth with various carbon and nitrogen sources and close to 80% for assimilation of aromatic compounds. Moreover, the M-model accurately predicts dynamic changes of growth and substrate consumption rates over time under nine chemoheterotrophic conditions and demonstrated high precision in predicting metabolic changes between photoheterotrophic and photoautotrophic conditions. This comprehensive M-model will help to elucidate metabolic processes associated with the assimilation of multiple carbon and nitrogen sources, anoxygenic photosynthesis, aromatic compound degradation, as well as production of molecular hydrogen and polyhydroxybutyrate.
In the Mexican Caribbean, marine protected areas have been established to tackle marine ecosystem degradation caused by the coastal development that started in Cancún in the 1970s and extended south ...to the border with Belize in the 1990s. It is crucial to assess their effectiveness for conservation of the reef ecosystem, but also the perception of stakeholders, because the objective would be unattainable without their participation.
This study evaluated the conservation status and the management effectiveness of National Park Xcalak Reefs (PNAX), in the southernmost Mexican Caribbean. In addition to interviewing local stakeholders to recognize issues related to the administration and functioning of PNAX, four zones with different use restrictions inside the park were evaluated, using ecological indicators (diversity and abundance of fishes, coral diversity and cover, and macroalgal cover) and ecological knowledge by interviewing local stakeholders, mostly fishers and conservation personnel.
The results suggest that one of the restricted‐use zones is in good condition, with a higher abundance of fishes and coral cover, and a lower cover of fleshy macroalgae and turf, compared with the other zones in the protected area. On the other hand, the core area presents bad indicators, such as a higher macroalgal cover and lower abundance of fishes, suggesting poor management or insufficient enforcement.
Although mistrust and lack of communication between fishers and conservation authorities may limit the achievement of conservation goals, some programmes involving active participation of local people, for example lionfish culling and coastal vegetation restoration, have had a good impact on the coral reef community.
The ammonia-oxidizing bacterium Nitrosomonas europaea has been widely recognized as an important player in the nitrogen cycle as well as one of the most abundant members in microbial communities for ...the treatment of industrial or sewage wastewater. Its natural metabolic versatility and extraordinary ability to degrade environmental pollutants (e.g., aromatic hydrocarbons such as benzene and toluene) enable it to thrive under various harsh environmental conditions. Constraint-based metabolic models constructed from genome sequences enable quantitative insight into the central and specialized metabolism within a target organism. These genome-scale models have been utilized to understand, optimize, and design new strategies for improved bioprocesses. Reduced modeling approaches have been used to elucidate Nitrosomonas europaea metabolism at a pathway level. However, genome-scale knowledge about the simultaneous oxidation of ammonia and pollutant metabolism of N. europaea remains limited. Here, we describe the reconstruction, manual curation, and validation of the genome-scale metabolic model for N. europaea, iGC535. This reconstruction is the most accurate metabolic model for a nitrifying organism to date, reaching an average prediction accuracy of over 90% under several growth conditions. The manually curated model can predict phenotypes under chemolithotrophic and chemolithoorganotrophic conditions while oxidating methane and wastewater pollutants. Calculated flux distributions under different trophic conditions show that several key pathways are affected by the type of carbon source available, including central carbon metabolism and energy production.
The synthesis of a Co metal-organic framework assembled from 5,10,15,20-tetrakis((pyridin-4-yl)phenyl)porphyrin; TPhPyP) "Co-MTPhPyP" is reported. The TPhPyP ligand was synthesized via aldehyde ...condensation in 28% yield and characterized by
H nuclear magnetic resonance (
H NMR), Fourier-transform infrared (FTIR), high-resolution mass spectrometry (HRMS), and UV-visible spectroscopy (UV-vis). Co-MTPhPyP was prepared by the solvothermal method from TPhPyP and CoCl
·H
O in 55% yield and characterized by X-ray powder diffraction (XRD), FTIR, thermogravimetric analysis (TGA), field-emission scanning electron microscopy with energy-dispersive X-ray (FESEM-EDS), X-ray photoelectron spectroscopy (XPS), and dynamic light scattering (DLS), showing a particle size distribution of 418 ± 58 nm. The sorption properties of the Co-MTPhPyP for the effective removal of Pb(II) and Cu(II) were evaluated in an aqueous medium and Cthe results showed uptake capacities of 383.4 and 168 mg of the metal g
after 2 h, respectively. Kinetic studies of Pb(II) adsorption by Co-MTPhPyP were adjusted to the pseudo-second-order model with a maximum adsorption capacity of 458.8 mg g
at 30 min of exposition.
From mid-2014 until the end of 2015, the Mexican Caribbean coast experienced a massive influx of drifting Sargassum spp. that accumulated on the shores, resulting in build-up of decaying beach-cast ...material and near-shore murky brown waters (Sargassum-brown-tides, Sbt). The effects of Sbt on four near-shore waters included reduction in light, oxygen (hypoxia or anoxia) and pH. The monthly influx of nitrogen, and phosphorus by drifting Sargassum spp. was estimated at 6150 and 61kgkm−1 respectively, resulting in eutrophication. Near-shore seagrass meadows dominated by Thalassia testudinum were replaced by a community dominated by calcareous rhizophytic algae and drifting algae and/or epiphytes, resulting in 61.6–99.5% loss of below-ground biomass. Near-shore corals suffered total or partial mortality. Recovery of affected seagrass meadows may take years or even decades, or changes could be permanent if massive influxes of Sargassum spp. recur.
•Massive onshore buildups of drifting Sargassum spp. cause Sargassum brown tides (Sbt).•Sbt cause reduction in light and oxygen in near-shore waters.•Sbt resulted in mortality of near-shore seagrasses, associated fauna and corals.•Long-term effects of Sbt include eutrophication of coastal waters.•Recovery of impact by Sbt may take decades.
This study evaluated the effect of zero-valent iron nanoparticles (NZVI) on the anaerobic digestion of swine manure. A wide range of doses of NZVI was evaluated (5, 10, 15, 20, 25, 50, and 100 ...mgFe°/gVS). The maximum methane yield of 0.4506 L/gVSremoved was obtained with the concentration of 10 mgFe°/gVS representing an increase of 58.99% than the control system with 0.2834 L/gVSremoved, indicating that Fe° improves the methanogenic activity. However, when using doses greater than 20 mgFe°/gVS, there were decreases in the methane yield of 34.4-47.98%. Also, to observe the effect of NZVI in anaerobes was evaluated the activity in the electron transport system (ETS), where the control reactor showed an activity of 31.91 μg INTred/gVS•h, while in reactors with NZVI showed values of 39.48 μg INTred/gVS•h (10 Fe°mg/gVS), observing a stimulation of Fe° in microbial activity. However, the dose of 100 mgFe°/gVS showed the greatest decrease in methane yield (0.1474 L/gVSremoved) and a reduction in ETS was observed by 8.5% compared to the control. The effect on the composition of the volatile fatty acids was observed, where the control system obtained a maximum production of acetic acid of 639 mg/L, which was exceeded with the dose of 10 mg Fe°/gVS by 215% and a decrease of 41.15% with the inhibitory concentration of 100 mg Fe°/gVS. As a result, higher doses of NZVI affect the metabolic activity of anaerobes as well as the acetoclastic pathway causing a decrease in the methane production.
Phenolic compounds with antioxidant properties are highly sensitive molecules, which limits their application. In response, extruded esterified starch has been proposed as efficient encapsulating ...material. In this work, we aim to describe the encapsulation of red sorghum phenolic compounds by spray drying using extruded phosphorylated, acetylated and double esterified sorghum starch as wall material. Their respective encapsulation yields were 77.4, 67.4 and 56.8%, and encapsulation efficiency 91.4, 89.7 and 84.6%. Degree of substitution confirmed esterification of the sorghum starch and Fourier transform infrared spectroscopy showed the significant chemical and structural changes in the extruded esterified starch loaded with phenolic compounds. Microcapsules from phosphorylated sorghum starch showed the highest endothermic transition (173.89 °C) and provided a greater protection of the phenolic compounds during storage at 60 °C for 35 days than the other wall materials. Extruded esterified sorghum starch proved to be effective material for the protection of phenolic compounds due to its high encapsulation efficiency and stability during storage.
Anaerobic digestion (AD) is the most widely used method to stabilize and recover energy from waste activated sludge (WAS). However, AD of sludge results in a low biogas yield. Ultrasonic pretreatment ...(USp) is the most effective sludge disintegration technology and has elicited interest to increase the biodegradability and improve the efficiency of the AD. This study investigated the influence of USp on the semicontinuous AD of WAS as a strategy to increase its performance. During an experiment lasting 90 days, 0.8-L digesters were semicontinuously fed under different conditions: raw sludge and sonicated at 15000, 25000 and 35000 kJ/kg TS (total solids); and an increase of the organic loading rate (OLR) from 1 to 3 kgVS/m3·d, for 30 days each. The maximum biogas rate (0.218 L/d) was reached at 25000 kJ/kg TS and 3 kgVS/m3·d. The highest VS removal efficiency (23.7%) was observed at the highest USp and the lowest OLR. The reactors fed with raw sludge had a lower performance compared to the sonicated WAS in terms of VS reduction and biogas production. In contrast, the USp allowed the bioreactors to be operated at a high OLR (3 kgVS/m3·d) without inhibition. Finally, a kinetic analysis of accumulated biogas was performed.
•The effects of USp on the semicontinuous AD of sludge were studied.•Different specific energies and organic loading rates were evaluated.•Ultrasonic pretreatment allowed reactors to operate at a high OLR (3 kgVS/m3·d).•The maximum biogas rate (0.218 L/d) was reached at 25000 kJ/kg TS and 3 kgVS/m3·d.
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•Nanoferrosonication (NFS) pretreatment was studied.•NFS was evaluated to improve the solubilization and anaerobic digestion of sludge.•Anaerobic tests were conducted at 15,000 and ...25,000 kJ/kgTS with 2 and 7 mgFe0/gVS.•The biogas yield increased from 106 to 308 mL/gVS with 7 mgFe0/gVS + 15,000 kJ/kgTS.•The results demonstrated that NFS was effective in intensifying the process.
In this work, the effect of coupling ultrasonic pretreatment with dosing of zero-valent iron nanoparticles (nanoferrosonication, “NFS”) to improve the anaerobic digestion of sewage sludge was studied. Biochemical methane potential tests were conducted at 15,000 and 25,000 kJ/kgTS and their combinations with 2 and 7 mgFe0/gVS. The biogas yield increased from 106 (control) to 143 (25,000 kJ/kgTS) and 308 mL/gVS with NFS (7 mgFe0/gVS + 15,000 kJ/kgTS). The methane content increased from 55.6 to 66%, and the maximum VS removal was 11.5% at 7 mgFe0/gVS + 15,000 kJ/kgTS. The results demonstrated that NFS was effective in intensifying the process.
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