Browsing by Author "Saez-Navarrete, Cesar"

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    An exploratory study of peat and sawdust as enhancers in the (bio)degradation of n-dodecane
    (2008) Saez-Navarrete, Cesar; Gelmi, Claudio A.; Reyes-Bozo, Lorenzo; Godoy-Faundez, Alex
    Current practice for dealing with oil spills involves the use of adsorbent materials to contain the pollution prior to bioremediation of the contaminated soil and adsorbent. This work presents a study of the effects of bioavailable carbon sources in the adsorbents peat and sawdust as organic nutrients for microorganisms specialized in degrading n-dodecane in soil and sawdust contaminated with hydrocarbon mixtures. An experimental bioremediation system was developed using n-dodecane, biomass adapted to n-dodecane, inorganic nutrients and the two adsorbents (sterilized). Bioreactors containing peat enhanced cell growth the most and also evolved more CO2. An advantage of peat is that its soluble carbon sources can sustain higher cell densities compared to sawdust, and this may prove decisive when cultivating endogenous microorganisms for the aerobic bioremediation of soils contaminated with hydrocarbons. However, at the end of the 68-day experiment slightly higher n-dodecane removal was identified in the system containing sawdust-n-dodecane (99.6%) than in that with peat-n-dodecane (98.5%), evidencing the higher hydrocarbon retention capacity of peat. Based on this study, the use of sawdust instead of peat is recommended when an adapted inoculum is available for aerobic bioremediation of organic contaminants, whereas the use of peat is advisable to boost cell densities in order to improve the probability of sustaining a viable biomass in unfavorable conditions.
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    Bacterial networks in Atlantic salmon with Piscirickettsiosis
    (Springer Nature, 2023) Coca Rives, Yoandy; Godoy, Marcos; Pontigo, Juan Pablo; Caro, Diego; Maracaja-Coutinho, Vinicius; Arias-Carrasco, Raul; Rodriguez-Cordova, Leonardo; de Oca, Marco Montes; Saez-Navarrete, Cesar; Burbulis, Ian
    An unbalanced composition of gut microbiota in fish is hypothesized to play a role in promoting bacterial infections, but the synergistic or antagonistic interactions between bacterial groups in relation to fish health are not well understood. We report that pathogenic species in the Piscirickettsia, Aeromonas, Renibacterium and Tenacibaculum genera were all detected in the digesta and gut mucosa of healthy Atlantic salmon without clinical signs of disease. Although Piscirickettsia salmonis (and other pathogens) occurred in greater frequencies of fish with clinical Salmonid Rickettsial Septicemia (SRS), the relative abundance was about the same as that observed in healthy fish. Remarkably, the SRS-positive fish presented with a generalized mid-gut dysbiosis and positive growth associations between Piscirickettsiaceae and members of other taxonomic families containing known pathogens. The reconstruction of metabolic phenotypes based on the bacterial networks detected in the gut and mucosa indicated the synthesis of Gram-negative virulence factors such as colanic acid and O-antigen were over-represented in SRS positive fish. This evidence indicates that cooperative interactions between organisms of different taxonomic families within localized bacterial networks might promote an opportunity for P. salmonis to cause clinical SRS in the farm environment.
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    Experimental and theoretical study of synthesis and properties of Cu2O/ TiO2 heterojunction for photoelectrochemical purposes
    (2023) Matamala-Troncoso, Felipe; Saez-Navarrete, Cesar; Mejia-Lopez, Jose; Garcia, Griselda; Rebolledo-Oyarce, Jose; Nguyen, Cuong Ky; MacFarlane, Douglas R.; Isaacs, Mauricio
    The Cu2O/TiO2 heterojunction is an attractive surface for its optoelectronic properties for developing catalysts, cells, and solar devices. However, the mechanisms involved in synthesizing an electrode using the Cu2O/TiO2 heterojunction can affect the surface properties and the surface/electrolyte interactions. In this work, we studied the formation mechanism of the Cu2O/TiO2 heterojunction by electrochemical deposition (ECD) of Cu2O mol-ecules on TiO2 nanoparticles previously deposited on a fluorine-doped thin oxide coated glass substrate (FTO). The photoelectrochemical properties of the Cu2O/TiO2/FTO electrode were characterized by XRD, FE-SEM, TEM, EDX, UV-vis diffuse reflectance spectroscopy (DRS), Raman spectroscopy, and electrochemical methods. Theoretical methods such as ab-initio density functional theory calculations and molecular dynamics simulations were used to understand the experimental results. The analysis carried out by theoretical methods allowed us to identify the initial steps of the formation mechanism of Cu2O molecules on TiO2 nanoparticles. Theoretical calculations demonstrated that forming a Cu2O nanowire-like network on the TiO2 nanoparticle matrix favors the charge transfer at the electrolyte/semiconductor interface, promoting the behavior of the electrode as a cathode. Finally, the Cu2O/TiO2/FTO electrode synthesized was used to perform the reduction photoelectrocatalyzed of nitrate to ammonia under illumination with a Xe-Hg arc lamp and applying-0.5 V bias potential (vs Ag/AgCl sat.) to evaluate the performance of the electrode as a cathode.
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    Facile methodology to generate Cu2O/TiO2 heterojunction on FTO electrode for photoelectroreduction of nitrate
    (2021) Matamala-Troncoso, Felipe; Nguyen, Cuong Ky; MacFarlane, Douglas R.; Isaacs, Mauricio; Saez-Navarrete, Cesar
    Easy and low-cost synthesis of a Cu2O/TiO2/FTO electrode is proposed. The Cu2O/TiO2 heterojunction was synthesized by sintering TiO2 nanoparticles on an FTO electrode surface, followed by a Cu2O electrochemical deposition step. Characterization of the electrode was performed by FE-SEM-EDX microscopy, Raman and UV-Vis DR spectroscopy, and electrochemical methods. The photoelectrochemical behavior was characterized, and the p-type character material was confirmed. The reduction of nitrate to nitrite was performed using the Cu2O/TiO2/FTO electrode under Xe lamp illumination with lower overpotentials than those commonly used in this electrochemical process. Nitrate/nitrite conversion was achieved with a promising result of about 22% conversion at-0.05 V RHE. (C) 2021 Elsevier B.V. All rights reserved.
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    Salmo salar Skin and Gill Microbiome during Piscirickettsia salmonis Infection
    (2024) Godoy, Marcos; Coca, Yoandy; Suarez, Rudy; Montes de Oca, Marco; Bledsoe, Jacob W.; Burbulis, Ian; Caro, Diego; Pontigo, Juan Pablo; Maracaja-Coutinho, Vinicius; Arias-Carrasco, Raul; Rodriguez-Cordova, Leonardo; Saez-Navarrete, Cesar
    Maintaining the high overall health of farmed animals is a central tenant of their well-being and care. Intense animal crowding in aquaculture promotes animal morbidity especially in the absence of straightforward methods for monitoring their health. Here, we used bacterial 16S ribosomal RNA gene sequencing to measure bacterial population dynamics during P. salmonis infection. We observed a complex bacterial community consisting of a previously undescribed core pathobiome. Notably, we detected Aliivibrio wodanis and Tenacibaculum dicentrarchi on the skin ulcers of salmon infected with P. salmonis, while Vibrio spp. were enriched on infected gills. The prevalence of these co-occurring networks indicated that coinfection with other pathogens may enhance P. salmonis pathogenicity.
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    Mayten Tree Seed Oil: Nutritional Value Evaluation According to Antioxidant Capacity and Bioactive Properties
    (2021) Ginocchio, Rosanna; Munoz-Carvajal, Eduardo; Velasquez, Patricia; Giordano, Ady; Montenegro, Gloria; Colque-Perez, German; Saez-Navarrete, Cesar
    The Mayten tree (Maytenus boaria Mol.), a native plant of Chile that grows under environmentally limiting conditions, was historically harvested to extract an edible oil, and may represent an opportunity to expand current vegetable oil production. Seeds were collected from Mayten trees in north-central Chile, and seed oil was extracted by solvent extraction. The seed oil showed a reddish coloration, with quality parameters similar to those of other vegetable oils. The fatty acid composition revealed high levels of monounsaturated and polyunsaturated fatty acids. Oleic and linoleic acids, which are relevant to the human diet, were well represented in the extracted Mayten tree seed oil. The oil displayed an antioxidant capacity due to the high contents of antioxidant compounds (polyphenols and carotenoids) and may have potential health benefits for diseases associated with oxidative stress.
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    Microbiome Dynamics of Salmo salar Skin and Gill
    (2023) Godoy, Marcos; Coca, Yoandy; Suarez, Rudy; de Oca, Marco Montes; Bledsoe, Jacob W.; Burbulis, Ian; Caro, Diego; Pontigo, Juan Pablo; Maracaja-Coutinho, Vinicius; Arias-Carrasco, Raul; Rodriguez Cordova, Leonardo Andres; Saez-Navarrete, Cesar
    Maintaining the high overall health of farmed animals is a central tenant of their well-being and care. Intense animal crowding in aquaculture promotes animal especially in the absence of straightforward methods for monitoring their health. Here, we used bacterial 16S ribosomal RNA gene sequencing to measure population dynamics occurring during P. salmonis outbreaks. Our findings revealed a complex bacterial community consisting of a previously undescribed core pathobiome. Notably, we detected Aliivibrio wodanis and Tenacibaculum dicentrarchi on the skin ulcers of salmon infected with P. salmonis, while Vibrio spp. were enriched on infected gills. The prevalence of these co-occurring networks indicates the influence that coinfection plays in P. salmonis pathogenicity.
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    Rougher flotation of copper sulphide ore using biosolids and humic acids
    (2011) Reyes-Bozo, Lorenzo; Herrera-Urbina, Ronaldo; Saez-Navarrete, Cesar; Otero, Alfonso F.; Godoy-Faundez, Alex; Ginocchio, Rosanna
    In the quest of new, less hazardous, and more ambient-friendly froth flotation reagents, the use of biosolids or humic acids as both collector and frother for the concentration of copper sulphide ores was investigated. Rougher flotation tests were conducted in Denver cells on a laboratory scale, and metallurgical indicators such as copper recovery, copper concentrate grade, and concentration and enrichment ratios were compared with those obtained under similar conditions but using conventional collectors and frothers for the industrial flotation of copper sulphide ores. With a dosage of 10% (w/w) biosolids, copper recovery and grade were 26% and 0.81%, respectively. The copper recovery and grade obtained with 1.5% (w/w) salt of humic acids were 29.7% and 3.5%, respectively. A significantly higher copper recovery (65.1%) was obtained with conventional industrial collectors and frothers, but the grade was also low (3.1% Cu). With the same dosage of humic substances, humic acid show that the flotation rate constant was significantly higher (0.2 min(-1)) than that obtained with the same dosage of biosolids (0.09 min(-1)). These results indicate that humic acids have more affinity than biosolids for copper-containing mineral species, and also show that biosolids and humic acids could be used as both collector and frother in the sulphide mineral concentration process by froth flotation. Because the distribution of iron in the concentrate obtained with biosolids is highest, these materials seem to have more affinity for pyrite. (C) 2011 Elsevier Ltd. All rights reserved.