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This chapter aims to present the fundamentals, important variables, and pharmaceuticals removed by ozonation and Fenton, which are only two of the current existing advanced oxidation processes. Some toxicological information regarding pharmaceuticals oxidized by ozonation is also included. Some strategies to improve such processes, like adding a catalyst, light, or electrical current, are also analyzed. Thus, this chapter intends to present general but fundamental aspects of the aforementioned processes.
"Indole is a bicyclic signaling molecule with effects on both eukaryotic and prokaryotic cells. The majority of studies of indole action have been performed with bacteria cultured under aerobic conditions and little information is available about its effects under anaerobic conditions. Here the effect of the indole on anaerobic metabolism of Escherichia coli WDHL was studied. Indole in the range 0.5–8 mM was added to the culture medium and cell growth, hydrogen and metabolite production were compared to cultures lacking indole. Results showed that while 8 mM indole abolished growth completely, 4 mM indole had a partial bacteriostatic effect and the maximum optical density of the culture decreased by 44% compared to the control cultures. In addition, 4 mM indole had an important effect on anaerobic metabolism. Hydrogen production increased from 650 ± 115 to 1137 ± 343 mL H2/L, and hydrogen yield increased from 0.45 ± 0.1 to 0.94 ± 0.34 mol H2/mol glucose, compared to the control culture. Carbon flux was also affected and the composition of the final by-products changed. Lactate (41 mM) was the main metabolite in the control cultures, whereas ethanol (56.2 mM) and acetate (41.2 mM) were the main metabolites in the cultures with 2 mM indole. We conclude that the supplementation of E. coli cultures with exogenous indole is a simple and novel strategy to improve the production of hydrogen as well as other metabolites such as ethanol used as biofuels."
"In this study, the simultaneous production of hydrogen, ethanol, and 2,3-butanediol was assessed using three agro-industrial residues: cheese whey powder (CWP), wheat straw hydrolysate (WSH) and sugarcane molasses (SCM), by the Antarctic psychrophilic GA0F bacterium [EU636050], which is closely related to Pseudomonas antarctica [KX186936.1]. The main soluble metabolites produced in all the fermentations were ethanol and 2,3-butanediol. CWP demonstrated to be the most effective carbon source, since fermentation of this substrate resulted in the highest yields of H2 (73.5 ± 10 cm3 g−1), ethanol (0.24 ± 0.03 g g−1) and 2,3-butanediol (0.42 ± 0.04 g g−1), followed by the use of SCM, whereas WSH showed to have an inhibitory effect during the fermentation process, showing the lowest production values. Our results demonstrated the ability of the Antarctic psychrophilic GA0F bacterium to produce valuable products using low-cost substrates at room temperature conditions."
BENITO SERRANO ROSALES (2019)
Six different Ni-based fluidizable catalysts were synthesized using both incipient impregnation and co-
impregnation. Ni-based catalysts were also promoted with 2.0 wt% La or alternatively with 2 wt% Ce. The
preparation procedure included catalysts treated at high temperatures and under free of oxygen conditions.
Catalysts were characterized using BET, XRD, AA, PSD, TPR, TPD, H2-chemisorption. TPR and H2 chemisorp-tion showed good metal dispersion with 10 nm- 40 nm metal crystallites.
Glucose catalytic gasification runs were performed in a CREC Riser Simulator to evaluate the following cata-
lysts: (a) 5 %Ni/γ-Al2O3, (b) 5 %Ni-2 %La/γ-Al2O3 and (c) 5 %Ni-2 %Ce/γ-Al2O3. In all cases, the preparation
steps involved acid solutions with pHs of 1 and 4. In between consecutive runs, different approaches were
considered: (a) A catalyst was regenerated by air, (b) A catalyst was regenerated by air followed by hydrogen
pretreatment, (c) A catalyst was reused directly without any regeneration or hydrogen pretreatment. It was
observed that Ni-based catalysts, which were subjected after every run, to both, air regeneration and hydro-
gen pretreatment, displayed the best yields in close agreement with thermodynamic equilibrium. On the other
hand, Ni-based catalysts regenerated with air only, showed the worst hydrogen yields. In between these two-
hydrogen yield limits, where catalysts not contacted with air nor hydrogen, with these yields being moderately
below chemical equilibrium.
This shows that Ni-based fluidizable catalysts can perform on stream for extended periods, requiring limited
reactivation with air and H2. This makes of gasification using the catalysts of the present study, a viable process alternative that could be implemented at industrial scale.
Producción Científica de la Universidad Autónoma de Zacatecas UAZ
"The impact of nitrogen source on hydrogen production by Escherichia coli WDHL (Delta hycA Delta lacI) strain using cheese whey as a substrate was evaluated. To improve the assimilation of complex proteins such as lactalbumin, we assessed treatment with a protease. Also, five external nitrogen sources were tested: NH4Cl, (NH4)(2)SO4, urea, yeast extract, and tryptone. The treatments in 120 mL serological bottles with pancreatin 1000 mg/L produced 1.75-fold more hydrogen than the cultures without pancreatin. In the bottle cultures supplemented with yeast extract or tryptone 5 g/L, hydrogen production increased up to 3.2- and 3.5-fold, respectively, whereas inorganic salts and urea had no statistical difference with respect to the control cultures. In 1-L bioreactors, the use of tryptone improved 2.1-fold hydrogen production. Tryptone or yeast extract enable the total consumption of lactose in 40 h, whereas in the control assay the lactose was not completely consumed. Our results demonstrate that it is necessary to select an adequate nitrogen source, which allows both carbon source consumption and high hydrogen production."
"Biological hydrogen production is an active research area due to the importance of this gas as an energy carrier and the advantages of using biological systems to produce it. A cheap and practical on-line hydrogen determination is desired in those processes. In this study, an artificial neural network (ANN) was developed to estimate the hydrogen production in fermentative processes. A back propagation neural network (BPNN) of one hidden layer with 12 nodes was selected. The BPNN training was done using the conjugated gradient algorithm and on-line measurements of dissolved CO2, pH and oxidation-reduction potential during the fermentations of cheese whey by Escherichia coli ΔhycA ΔlacI (WDHL) strain with or without pH control. The correlation coefficient between the hydrogen production determined by gas chromatography and the hydrogen production estimated by the BPNN was 0.955. Results showed that the BPNN successfully estimated the hydrogen production using only on-line parameters in genetically modified E. coli fermentations either with or without pH control. This approach could be used for other hydrogen production systems."
"Biologically produced hydrogen (biohydrogen) is a valuable gas that is seen as a future energy carrier, since its utilization via combustion or fuel cells produces pure water. Heterotrophic fermentations for biohydrogen production are driven by a wide variety of microorganisms such as strict anaerobes, facultative anaerobes and aerobes kept under anoxic conditions. Substrates such as simple sugars, starch, cellulose, as well as diverse organic waste materials can be used for biohydrogen production. Various bioreactor types have been used and operated under batch and continuous conditions; substantial increases in hydrogen yields have been achieved through optimum design of the bioreactor and fermentation conditions. This review explores the research work carried out in fermentative hydrogen production using organic compounds as substrates. The review also presents the state of the art in novel molecular strategies to improve the hydrogen production."
Anaerobic conditions Biohydrogen Biomass Bioreactor Dark fermentation Gene manipulation Hydrogenases Hydrogen production Mixed culture CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA
"Fermentations of lactose, glucose and galactose using Escherichia coli WDHL, a hydrogen over producer strain, were performed. With glucose as substrate pyruvate was mainly routed to the lactate pathway, resulting in hydrogen production and yield of 1037 mL and 0.30 mol H2/mol of glucose, respectively. When galactose was the substrate, the pyruvate formate lyase pathway was the main route for pyruvate and a fermentation yield of 1.12 mol H2/mol of galactose and a hydrogen production of 2080 mL were obtained. The fermentation of lactose or glucose plus galactose showed a similar yield of 1.02 mol H2/mol of hexose consumed. This work clearly demonstrated that the kinetics of hydrogen and metabolites production as well as the hydrogen yield were affected by the type of sugar used as substrate as reflected by the deviations from the metabolic hydrogen-production pathway."
"Hydrogen is an attractive energy carrier because of its high energy density, and used as a raw material in various chemical processes. Nowadays, hydrogen demand is supplied from non-renewable sources, and alternative sources are becoming mandatory. Hydrogen production by biological methods uses renewable resources as substrate and its production occurs at ambient temperature and atmospheric pressure. Thus, it is less energy intensive than the chemical and thermochemical methods used to produce hydrogen. This review is focused on fermentative hydrogen production by Escherichia coli. The hydrogen production pathway, the genetic manipulations, and expression of non-native pathways into this microorganism are reviewed. The hydrogen production using alternative substrates is a critical point to develop sustainable process by this reason the principal substrates for hydrogen production using E. coli are revised. Other strategies like two stages processes and immobilized cells are also discussed."
In this work the electrical characterization of n-channel a-SiGe:H TFTs with planarized gate electrode is presented. The planarized a-SiGe:H TFTs were fabricated at 200°C on corning glass substrate. The devices exhibit a subthreshold slope of 0.56 V/Decade, an on/off-current ratio approximately of 10⁶ and off-current approximately of 0.3x10⁻¹² A. The results show an improvement of the electrical characteristics when are compared to those unplanarized devices fabricated at higher temperature. Moreover, the simulation of the device using a SPICE model is presented.