The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. http://pantheon.ufrj.br:80 2026-03-17T00:37:41Z 2026-03-17T00:37:41Z Monteiro Junior, Willian Bastos http://hdl.handle.net/11422/28895 2026-03-16T22:19:51Z 2025-12-08T00:00:00Z

Title: Produção de etanol a partir do hidrolisado de milho extrudado: comparação entre as cepas cat-1 e ethanol red de Saccharomyces cerevisiae Author(s)/Inventor(s): Monteiro Junior, Willian Bastos Advisor: Leitao, Viridiana Santana Ferreira Abstract: The growing demand for renewable sources has driven ethanol production and consolidated Brazil among the world’s leading producers. Although sugarcane remains the foundation of the sugar-energy sector, corn has gained prominence as a complementary feedstock, especially in the Midwest, due to the wide availability of the second harvest and its ease of storage. The high starch content of this grain favors its enzymatic conversion into glucose and maltose, a process that can be intensified by pretreatments such as dry extrusion. In this context, there is increasing interest in fermentation processes under very high gravity (VHG) conditions, which operate with concentrations above 250 g/L of glucose. These conditions increase productivity and final ethanol concentration but impose intense osmotic stress on yeast, requiring robust strains. Given this scenario, the present study aimed to understand the fermentative behavior of the industrial strains Saccharomyces cerevisiae CAT-1 and Ethanol Red and to propose an alternative process for ethanol production from extruded corn without additional nutritional supplementation. To this end, the study was structured in sequential stages, beginning with preliminary fermentation assays and advancing to the application of real hydrolysates under high-solids conditions. Initially, kinetic assays were conducted in synthetic YPD medium containing different glucose concentrations (150, 200, 295, and 320 g/L), inoculated with 1 g/L of cells, to assess strain performance under normal gravity (NG), high gravity (HG), and VHG conditions. Ethanol Red demonstrated greater osmotolerance, reaching higher ethanol concentrations in VHG media compared to CAT-1, establishing a basis for subsequent experiments. During characterization of the enzymatic hydrolysate from extruded corn, maltose was detected, indicating incomplete starch hydrolysis. Therefore, complementary assays were performed in synthetic media containing mixtures of glucose and maltose (150 g/L total sugars) to evaluate the strains’ ability to ferment both carbohydrates. CAT-1 was able to assimilate maltose, although less efficiently than Ethanol Red. However, the presence of this disaccharide reduced ethanol production in both strains. Based on these results, hydrolysates produced using different hydrolysis media (citrate buffer, phosphate buffer, and acidified water) were evaluated. Diluted hydrolysates (~250 g/L) were fermented by both strains to investigate the influence of the hydrolysis medium on fermentative performance. The best results were obtained with citrate and phosphate buffered hydrolysates, although ethanol concentrations remained below expectations. Considering the objective of maximizing yield and productivity without supplementation, the effect of increasing initial cell concentration (30 and 50 g/L) was evaluated in diluted hydrolysates. The best results occurred with 30 g/L inoculum in citrate-buffered syrup, producing 120 g/L (CAT-1) and 117 g/L (Ethanol Red). In undiluted syrup (~320 g/L) with 50 g/L inoculum, ethanol concentrations of 129 g/L (CAT-1, yield 0.31 g/g) and 99 g/L (Ethanol Red, yield 0.26 g/g) were obtained. At larger scale in 2-L bioreactors, ethanol concentrations reached 110 g/L (CAT-1) and 84 g/L (Ethanol Red), with efficiencies of 68.5% and 54.3%, respectively. Despite these advances and the demonstrated feasibility of VHG fermentation using extruded-corn hydrolysates, overall efficiency remained below the industrially desirable threshold (≥80%), indicating the need for further optimization. Publisher: Universidade Federal do Rio de Janeiro Type: Dissertação

2025-12-08T00:00:00Z Oliveira, Wallace Alves de http://hdl.handle.net/11422/28894 2026-03-16T22:01:03Z 2025-01-01T00:00:00Z

Title: A utilização de aplicativos como ferramenta pedagógica nas aulas de química Author(s)/Inventor(s): Oliveira, Wallace Alves de Advisor: Moreira, Leonardo Maciel Abstract: This dissertation investigates the potential and challenges of using mobile applications as a pedagogical tool in Chemistry teaching, focusing on the creation and analysis of two digital learning games (DGs): one about the Periodic Table and the other about Organic Functions. The study is based on the observation that students have difficulty understanding chemical content, largely due to content abstraction, and the need for innovative teaching practices that combine playfulness and technology. Given this context, the work proposes the use of play and digital technologies as an alternative to bring students closer to Chemistry concepts in an interactive and constructive manner. Based on Jean Piaget’s constructivist theories and on references such as Bruno Leite and Marlon Soares’s work on playfulness and Digital Information and Communication Technologies (DICT), it is emphasized that games act as tools for knowledge construction, promoting autonomy and creativity. To this end, the work adopts a qualitative and exploratory approach. The research was conducted in two stages: the first consisted of interviews with teachers who used free apps to develop JDD; the second involved the development and delivery of a mini-course with undergraduate Chemistry students at IFRJ – Duque de Caxias Campus, focused on creating JDD. The data were analyzed using Bardin’s Content Analysis, revealing that digital games promote engagement, autonomy, and meaningful learning, while highlighting challenges such as a lack of teacher training and technological infrastructure. The interviews highlighted teachers’ enthusiasm for innovation, while also highlighting limitations such as lack of time, institutional support, and technological training. In the second stage, analysis of the activities revealed five categories: pedagogical intentionality, structure and mechanics, aesthetics and digital language, pedagogical feasibility, and suggestions for improvement. The results demonstrated the educational potential of the experience, promoting critical reflection, creative autonomy, and professional development among future teachers. The study concludes that the use of apps in Chemistry teaching represents an important pedagogical practice, capable of integrating science, playfulness, and technology, expanding teaching and learning possibilities and contributing to the development of reflective and creative teachers. Publisher: Universidade Federal do Rio de Janeiro Type: Dissertação

2025-01-01T00:00:00Z Hellmann, Thauany http://hdl.handle.net/11422/28893 2026-03-16T21:48:40Z 2025-10-03T00:00:00Z

Title: Estrutura eletrônica, orientação molecular e organização em nanoescala de filmes finos de nanocompósitos de MoS2: uma abordagem espectroscópica Author(s)/Inventor(s): Hellmann, Thauany Advisor: Pereira, Maria Luiza Rocco Duarte Abstract: In this work, we carried out the spectroscopic characterization of thin films of nanocomposites based on molybdenum disulfide (MoS2) with polyaniline (PANI) and with graphene oxide (GO), obtained through the liquid–liquid interfacial method. MoS2/PANI nanocomposites were synthesized in different aqueous phases, varying the type of acid (H2SO4 and HCl) and the pH (pH 0 and pH 1). X-ray photoelectron spectroscopy (XPS) revealed higher doping levels in the nanocomposites compared to pure PANI, as well as C–S bonds indicating strong interaction with MoS2. Reflection electron energy loss spectroscopy (REELS) showed a reduction in the energy gap, attributed to the elongation of the polymer chains, influenced by the acid type and by the presence of MoS2. MoS2/PANI nanocomposites were also analyzed after aging, and XPS indicated PANI deprotonation and an intensification of interactions with MoS2. Synchrotron infrared nanospectroscopy (SINS) proved particularly effective in identifying chemical variations at the nanometric scale, highlighting the influence of pH and dopant type on the structure and organization of the films. Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, performed at the nitrogen K-edge, suggested the coexistence of protonated and deprotonated units, indicating partial deprotonation of the polymer. The variation of the incidence angle of the beam showed that molecular organization depends on the synthesis and deposition conditions of the samples. MoS2 and GO nanocomposites were obtained through three interfacial routes: (i) one-pot, (ii) two-step, and (iii) layer-by-layer. Photoemission spectra revealed C–S bonds, indicating chemical interaction between MoS2 and GO. The SINS technique mapped chemical heterogeneities associated with the synthetic route. Films obtained by layer-by-layer deposition showed greater resemblance to pure MoS2 films, whereas those obtained via one-pot and two-step routes exhibited characteristics closer to GO. NEXAFS measurements at the sulfur L2,3-edge indicated a higher degree of structural organization of MoS2 in the nanocomposites compared to the isolated material. The results demonstrate that both the interaction between components and the synthesis route impact the structural and electronic properties of the films, underscoring the importance of synthetic control in the development of new materials. Publisher: Universidade Federal do Rio de Janeiro Type: Tese

2025-10-03T00:00:00Z Fagundes, Ramon da Conceição http://hdl.handle.net/11422/28892 2026-03-16T21:25:35Z 2025-12-03T00:00:00Z

Title: Educação ambiental no ensino de química: propostas de oficinas socioambientais a partir da temática geradora resíduos, em diálogo com a perspectiva Discente~Docente~Aprendente Author(s)/Inventor(s): Fagundes, Ramon da Conceição Advisor: Tamiasso-Martinhon, Priscila Abstract: Currently, Brazil faces deregulation in the management of Municipal Solid Waste (MSW) and the worsening of socio-environmental inequalities, impacting environmental, social, economic, political, and educational structures. In this scenario, Critical Environmental Education (CEE) emerges in Chemistry teaching as an approach capable of problematizing MSW and promoting educational practices that articulate social and cultural dynamics, forming critical and emancipated subjects. This research aimed to develop, implement, and evaluate socio-environmental workshops for Middle School (MS) and High School (HS) classes, based on CEE, the UN 2030 Agenda, and the Sustainable Development Goals (SDGs), as well as to produce original teaching materials and establish spaces for dialogue from the Student~Teacher~Learner (S~L~L) perspective. The methodological approach adopted a qualitative, interventional approach with ethnographic contours. Three workshops were proposed and two were implemented, targeting 9th-grade elementary school classes and 1st and 2nd-year high school classes. Data collection instruments included questionnaires, student narratives, visual summaries, and other group productions. Each workshop presented distinct approaches, but centered on concrete and everyday issues, with waste as the central theme. Additionally, a teaching guide based on the S~L~L perspective was developed, allowing other educators to implement the workshops independently of their contexts. The results show that students were able to relate chemical content to MSW (Municipal Solid Waste), reflecting on consumption, inequalities, and environmental impacts, going beyond a conservationist approach. Social mobilization was observed, in which students perceived themselves as multipliers, taking the learning to their families and questioning the prevailing socio-environmental structures. Thus, the workshops provided critical-reflective training, bringing chemical knowledge closer to socio-environmental issues and contributing to the development of autonomous and multiplier individuals. Publisher: Universidade Federal do Rio de Janeiro Type: Dissertação

2025-12-03T00:00:00Z