► Methane production under the specific conditions in Mexico City was demonstrated. ► Enhanced performance was achieved with pH control and nitrogen addition. ► Co-digestion of FVW with meat residues ...allows high and stable performance (30L). ► The microbial population in the AD system during optimal performance was determined. ► Bacterial and Archaea populations were correlated with its function in the AD system.
This study evaluated the feasibility of methane production from fruit and vegetable waste (FVW) obtained from the central food distribution market in Mexico City using an anaerobic digestion (AD) process. Batch systems showed that pH control and nitrogen addition had significant effects on biogas production, methane yield, and volatile solids (VS) removal from the FVW (0.42mbiogas3/kgVS, 50%, and 80%, respectively). Co-digestion of the FVW with meat residues (MR) enhanced the process performance and was also evaluated in a 30L AD system. When the system reached stable operation, its methane yield was 0.25 (m3/kgTS), and the removal of the organic matter measured as the total chemical demand (tCOD) was 65%. The microbial population (general Bacteria and Archaea) in the 30L system was also determined and characterized and was closely correlated with its potential function in the AD system.
Two-stage process of dark fermentation (DF) and photo fermentation (PF), using fruit and vegetable waste (FVW) and cheese whey powder (CWP), was used as an approach to enhance the hydrogen (H2) ...production. FVW and CWP at C/N ratios of 34, 39, 60, 71 and 82 were tested as substrates for DF. Dilution (1:2, 1:5, 1:10) of the DF effluents was used as a coupling strategy. DF effluents with low-butyrate and high lactate concentrations were obtained as a function of an increased C/N ratio, which results in high H2 production during the PF. Maximum overall H2 yields of 793.7 and 695.4 mLH2/gChemical Oxygen Demand (COD) were obtained using a 1:10 dilution, at a C/N ratio of 60 and 70, respectively. These H2 yields were higher than those obtained with the individual processes. The C/N ratio at the DF stage regulate not only H2 production but also the distribution and concentrations of by-products. These metabolites, in turn, control the H2 production during the PF. Predominant microbial population for both processes (DF: C/N = 34 Acetobacter lovaniensis, Clostridium butyricum; C/N = 39 C. butyricum, Enterobacter sp, Bifidobacterium; C/N = 82 Lactobacillus casei; PF: Rhodopseudomonas palustris) were in accordance with the final metabolic products.
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•Enhanced H2 production by dark-photo (DF-PF) fermentations was demonstrated.•Fruit and vegetable waste and cheese whey as substrate allows waste removal and H2 production.•Increased C/N ratio reduces H2 yield at DF, but increase the H2 production at PF.•DF effluents with high lactate concentrations promotes high H2 production at PF.•Microbial population for both DF, PF in accordance with the final metabolic products.
Petroleum and fuel oil are complex mixtures of recalcitrant hydrocarbons. The biodegradation of these hydrocarbons needs the action of a vast variety of enzymatic capacities. A microbial consortium ...offers the capability to degrade complex substrates through the assembly of different biochemical reactions, providing a metabolic versatility superior to axenic cultures. In this work, the microbial population dynamics, taxonomy, and the catabolic capacity of a stabilized consortium exposed to fuel and crude oil was analyzed through metagenomics. The stabilized consortium degraded 59% of crude oil components after 8 days, and 34% of fuel oil components after 130 days. Population dynamics analysis indicates that in fuel oil the biodiversity richness was higher; however, denaturing gradient gel electrophoresis similarity dendrogram shows significant changes in the microbial population during crude oil degradation. Taxonomy studies indicate a great genera divergence; only eight microbial genera were common in both samples. In crude oil, the
Limnobacter
sp. was the most abundant specie (15.6%), while
Sphingomonas wittichii
(7.9%) and
Novosphingobium aromaticivorans
(7.6%) were abundant in fuel oil. These microorganisms have been reported to participate in the degradation of aliphatic and aromatic hydrocarbons. Functional analysis suggests that fuel and crude oil components changed the interactions between the consortium members affecting the collective metabolic functionality.
Hydrogen (H
2
) production from the organic fraction of solid waste such as fruit and vegetable waste (FVW) is a novel and feasible energy technology. Continuous application of this process would ...allow for the simultaneous treatment of organic residues and energy production. In this study, batch experiments were conducted using glucose as substrate, and data of H
2
production obtained were successfully adjusted by a logistic model. The kinetic parameters (
μ
max
= 0.101 h
−1
,
K
s
= 2.56 g/L) of an H
2
-producing microbial culture determined by the Monod and Haldane–Andrews growth models were used to establish the continuous culture conditions. This strategy led to a productive steady state in continuous culture. Once the steady state was reached in the continuous reactor, a maximum H
2
production of 700 mL was attained. The feasibility of producing H
2
from the FVW obtained from a local market in Mexico City was also evaluated using batch conditions. The effect of the initial FVW concentration on the H
2
production and waste organic material degradation was determined. The highest H
2
production rate (1.7 mmol/day), the highest cumulative H
2
volume (310 mL), and 25 % chemical oxygen demand (COD) removal were obtained with an initial substrate (FVW) concentration of 37 g COD/L. The lowest H
2
production rates were obtained with relatively low initial substrate concentrations of 5 and 11 g COD/L. The H
2
production rates with FVW were also characterized by the logistic model. Similar cumulative H
2
production was obtained when glucose and FVW were used as substrates.
•Increasing exposure in air produced more hydroxylated native oxide films on steel.•The passive film became increasingly more protective with age of native oxide film.•The passive films consist of a ...inner Fe(II)-rich layer and an outer FeOOH layer.•A kinetic model was reasonably optimized on the experimental impedance spectra.
Electrochemical impedance spectroscopy (EIS), open circuit potential (Eoc) measurements and angle-resolved X-ray photoelectron spectroscopy (AR-XPS) were used to investigate the effect of exposure in air on the passivation of carbon steel electrodes in a neutral aerated glutarate solution. The electrochemical measurements showed that for native oxide films aged between 4 h and 120 h the passive films became increasingly more protective. Analysis of the XPS revealed a bilayer structure of the passive film (inner Fe(II)-rich, outer Fe oxyhydroxide), with increasing values of the Fe(III)/Fe(II) intensity ratio, and gave evidence that passivation was favored by progressively hydroxylated native oxide films.
•Zincate treatment on Aluminum has an impact on the quality of the Ni-P deposit.•The speed of deposition impacts composition of Ni/P, higher rate resulted in less P.•Corrosion resistance of Ni-P ...depends on gas bubbled during the electrochemical tests.
AA6061 samples were coated with electroless Ni-P after a pretreatment which consisted of either single, double or triple zincating. It was observed that increasing the number of zincating reduces the amount of zinc on the surface, and this has a direct effect on the initial rate of deposition of the Ni-P coating, which was confirmed through pH measurements. The corrosion performance of uncoated and coated AA6061 was evaluated at open circuit conditions with conventional electrochemical techniques in 0.5 M H2SO4 solution bubbled with H2 or O2 to simulate the anodic and cathodic environments respectively of a Proton Exchange Membrane Fuel Cell (PEMFC). In both environments the corrosion rate was lower in the presence of Ni-P coating compared to uncoated AA6061 and it also decreased while increasing the zincate pretreatment steps. This latter effect was attributed to higher P content and amorphous nature of the coating. Furthermore, it was observed that for all coated samples the corrosion rate was higher in the simulated cathodic environment. Potentiostatic tests were also carried out to further discuss the stability of the coatings and the results showed that the measured current density followed the same trend as the corrosion current density. It decreased with increasing number of zincate steps in both environments. Also, measured currents were lower in the simulated anodic environment, confirming a better stability in the anodic side.
Plants are subject to different types of stress, which consequently affect their growth and development. They have developed mechanisms for recognizing and processing an extracellular signal. Second ...messengers are transient molecules that modulate the physiological responses in plant cells under stress conditions. In this sense, it has been shown in various plant models that membrane lipids are substrates for the generation of second lipid messengers such as phosphoinositide, phosphatidic acid, sphingolipids, and lysophospholipids. In recent years, research on lipid second messengers has been moving toward using genetic and molecular approaches to reveal the molecular setting in which these molecules act in response to osmotic stress. In this sense, these studies have established that second messengers can transiently recruit target proteins to the membrane and, therefore, affect protein conformation, activity, and gene expression. This review summarizes recent advances in responses related to the link between lipid second messengers and osmotic stress in plant cells.
The inhibition effect of sodium glutarate towards corrosion of carbon steel in neutral 0.02 M NaCl solution was investigated with potentiodynamic polarization and electrochemical impedance ...measurements. Results of electrochemical measurements revealed a poor inhibitive action for low concentrations (1 mM and 5 mM) and a significant improvement in efficiency for concentrations of 32 mM or higher. The protective film exhibited excellent stability in the temperature range 22°C–55°C. Full chemical passivation was accomplished and analysis of the impedance spectra for the high concentrations of glutarate was consistent with the inhibition mechanism which assumes that the carboxylates support the passivation of carbon steel in aerated solutions by plugging the defect sites and that the passivation process is enhanced by adsorption of the carboxylates on the oxide-covered surface. Such mechanism was confirmed by the XPS analysis.
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