TEDE Communidade:

Estudo da interação de diferentes bactérias na indústria do petróleo e seus metabólitos: monitoramento por microbiologia clássica e biologia molecular

2026-03-26T12:21:10Z

Título: Estudo da interação de diferentes bactérias na indústria do petróleo e seus metabólitos: monitoramento por microbiologia clássica e biologia molecular Autor: Montez, Gustavo Fabbri Primeiro orientador: Costa, Antonio Carlos Augusto da Abstract: The biogenic production of sulfide is one of the main problems of the oil and gas industry, causing corrosion in storage tanks and pipes. This is possible by injecting seawater during secondary oil recovery. In the present work, high levels of sulfate-reducing bacteria and acid-producing bacteria were detected in water / oil samples from various locations in the oil industry, as well as several other microbial groups. 35 samples were analyzed in a preliminary phase and in a second moment another 13 samples, where a wider range of microbial cells was detected. The water and oil samples that showed the highest microbial growth were submitted to metagenomic analysis, which confirmed the presence of a diversity of microorganisms, indicating the complexity of the consortium in the production of sulfide, based on the activity of acid-producing cells and associated species. It was also identified, through chromatographic analyzes, formic acid as a metabolite for the growth of acid-producing bacteria that will serve as a substrate for sulfate-reducing bacteria, thus creating a corrosion- friendly microbiome. Instituição: Universidade do Estado do Rio de Janeiro Tipo do documento: Tese

Determinação de elementos-traço em matrizes complexas por ICP OES e ICP-MS

2026-03-23T13:55:01Z

Título: Determinação de elementos-traço em matrizes complexas por ICP OES e ICP-MS Autor: Costa, Marina Araujo João Lopes da Primeiro orientador: Gois, Jefferson Santos de Abstract: The determination of trace elements in complex matrices presents challenges in chemical analysis due to interferences from major matrix components that compromise result accuracy and precision. This work presents analytical strategies to address such challenges using Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The thesis is divided into three chapters, each focusing on a specific matrix and related analytical issues in trace element determination: seawater, edible insects, and glycerin. The first study focuses on the preconcentration of As, Cu, and Pb in seawater, a matrix with high levels of dissolved salts that interfere with analysis. Using manganese oxide molecular sieve (OMS-2) as an adsorbent, the preconcentration process was optimized, achieving high enrichment factors and suitable detection limits for accurate metal quantification. The second study investigates the bioaccessibility of essential trace elements (Fe, Zn, and Cu) in different edible insect species using simulated in vitro digestion followed by ICP-MS detection. Results showed interspecies variability, with mealworms presenting the highest values. Complementary studies using Size Exclusion Chromatography (SEC) coupled with ICP-MS provided insights into the molecular weight of Fe, Zn, and Cu associated species during digestion, suggesting these ions are primarily bound to low-molecular-weight organic compounds. The third study developed a robust "dilute-and-shoot" method for trace metal determination in glycerin, a biodiesel byproduct. Due to its high viscosity and organic nature, glycerin requires an approach that minimizes non-spectral interferences. The validated method proved effective, ensuring the precision and accuracy needed for compliance with regulatory standards. Overall, the research offers effective solutions to analytical challenges in trace element determination in complex matrices, contributing to progress in industrial and scientific fields. Instituição: Universidade do Estado do Rio de Janeiro Tipo do documento: Tese

Avaliação da extração de celulose bacteriana a partir do resíduo de Kombucha (SCOBY): caracterização microbiológica, físico-química e aplicação como carga em composições de borracha

2026-04-14T19:38:35Z

Título: Avaliação da extração de celulose bacteriana a partir do resíduo de Kombucha (SCOBY): caracterização microbiológica, físico-química e aplicação como carga em composições de borracha Autor: Campeão, Fernanda de Andrade Buás Primeiro orientador: Sousa, Ana Maria Furtado de Abstract: Kombucha is a slightly carbonated fermented beverage produced from sweetened Camellia sinensis tea and a Symbiotic Culture of Bacteria and Yeasts (SCOBY, from the English, Symbiotic Culture of Bacteria and Yeast). At the end of production, this SCOBY is discarded as production waste or partially reused to generate new fermentations. The SCOBY is composed of bacterial cellulose, which in kombucha is known as Kombucha Cellulose (KC). KC has attracted growing interest in biotechnological applications. As a result, several studies have focused on its use in different industrial segments. Considering its high potential as a reinforcing filler, the present work aimed to evaluate the KC extraction process from SCOBY, perform its physicochemical characterization, and investigate its feasibility in natural rubber (NR) compositions. Additionally, microorganisms (bacteria and yeasts) were isolated and the microbial diversity of the SCOBY was characterized through metagenomic analysis. In the microbiological characterization, six bacteria were isolated, two of which had characteristics of Acetic Acid Bacteria (AAB), belonging to the genus Komagataeibacter sp., and two yeasts. The metagenomic analysis resulted in 24 bacteria and 6 fungi, with the most abundant bacterium being Komagataeibacter sucrofermentans and the yeast being Zygosaccharomyces bailii. Kombucha production yielded 3.83 g/L of SCOBY, with a sugar conversion rate of 0.078 g/g and an average productivity of 0.26 g/L·day. To evaluate cellulose extractions, the SCOBYs were treated by three methods: alkaline treatment with 1M NaOH (TA), autoclaving (AU), and a combination of both methods (AUTA). The compositional analysis assessed the three extraction methods and it was observed that the TA and AUTA methods promoted a greater reduction of 86% and 70% in lipids, respectively. In both cases, protein removal averaged 84%. Scanning electron microscopy (SEM) micrographs revealed that, in the TA extraction, the fibers were more dispersed and predominantly nanometric in diameter (<100 nm). On the other hand, the combination of both methods (AUTA) resulted in a more compact structure. Of all the extraction methods, TA was chosen as the treatment for using SCOBY in latex application. Freeze-dried and milled KC-TA samples were subjected to FTIR and XRD analyses, where KC showed characteristics of type I cellulose, with a crystallinity index of 58.4% and a maximum degradation peak of 315°C in TGA-DTG. KC was then added to latex in fractions of 0, 2.5, 5, 10, and 15 phr (parts per hundred). The addition of KC influenced the mechanical and structural properties of the rubber, resulting in a reduction in vulcanization time and an increase in torque, crosslink density, hardness, and tear resistance. However, it reduced elongation and tensile strength. Instituição: Universidade do Estado do Rio de Janeiro Tipo do documento: Dissertação

Eletrodos de grafeno 3D com óxidos de metais de transição para a reação de evolução de oxigênio

2026-03-31T17:02:51Z

Título: Eletrodos de grafeno 3D com óxidos de metais de transição para a reação de evolução de oxigênio Autor: Santana, Julia Magaly Costa de Primeiro orientador: Senna, Lilian Ferreira de Abstract: Given the growing demand for sustainable energy sources, water electrolysis has emerged as a promising alternative for green hydrogen production. However, the efficiency of this process is hindered by the oxygen evolution reaction (OER), which suffers from sluggish kinetics and a high overpotential. In this context, this work proposes the development of electrocatalysts based on three-dimensional graphene (3D-G), combined with iron oxides featuring core–shell structures and mixed oxides, aiming to enhance the electrocatalytic activity and electrode stability in alkaline media. Composite electrodes with core–shell structures (α-Fe₂O₃@C and Fe₃O₄@C) and the mixed oxide CoFe₂O₄ anchored onto 3D graphene were synthesized. Physicochemical analyses confirmed the successful formation of the targeted materials, with good oxide dispersion and the presence of a carbonaceous shell, contributing to increased surface area. Electrochemical tests revealed that the G3DFe₃O₄@C and G3DCoFe₂O₄ electrocatalysts exhibited excellent performance toward OER, achieving a current density of 10 mA·cm⁻² with low overpotentials below 300 mV. Furthermore, they showed low Tafel slopes (39.9 and 43.6 mV·dec⁻¹, respectively) and reduced charge transfer resistance (Rct), as demonstrated by electrochemical impedance spectroscopy (EIS). Therefore, the developed electrocatalysts are considered effective, affordable, and promising alternatives for the oxygen evolution reaction (OER). Instituição: Universidade do Estado do Rio de Janeiro Tipo do documento: Dissertação