Browsing by Author "Scott, Felipe"

Now showing 1 - 17 of 17
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    (33, 33) Saleh-Cumsille, Javier; Cruz, Pedro; Huiliñir, Cesar; Scott, Felipe; Vergara-Fernández, Alberto; 33
    BACKGROUND: This article proposes a new methodology for calculating kLa in airlift reactors (ALRs) based on a digital imaging technique and Higbie's model. Four ARLs with different internal diameters (28, 37.4, 45, and 55 mm) were used to determine the aeration patterns, velocities, and size distributions of the bubbles. Video recordings lasting 10 s were recorded using a 1080p slow-motion camera at 240 frames per second (fps). In 100 frames per video, between 500 and 599 frames, the characteristics of the bubbles were captured and then processed using the sci-kit-image Python package. RESULTS: The Higbie model coupled with image analysis was used to determine kL, and was then compared with the experimental values and kLa correlations. As a result, bubble velocities between 0.2 and 0.8 m s?1 were determined. CONCLUSIONS: The kLa values (20–28 h?1) calculated using the new methodology were close to the experimental values and were compared with the correlations for ALRs.
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    (33, 33) San Martin-Davison, Jessica; Scott, Felipe; Vergara-Ojeda, Christian; Moreno-Casas, Patricio; Hort, Cecile; Vergara-Fernández, Alberto; 33
    BACKGROUND: Indoor air pollution is a growing problem worldwide that causes a series of health issues in the population. Effective devices for abatement of volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) are currently restricted to adsorption systems based on active carbon. The objective of this study was to evaluate the operation of a new design of radial-flow biopurifier using a model mixture of toluene, benzo(?)pyrene (BaP) and formaldehyde, initially inoculated with the filamentous fungus Fusarium solani and the bacterium Rhodococcus erythropolis. RESULTS: The results show that, under the range of inlet load tested and under continuous operation, the biopurification system achieved removal efficiencies above 90%, translating into a purifier air refreshment capacity of 0.62, 2.5 and 0.8 h?1 for BaP, formaldehyde and toluene, respectively. CONCLUSION: The system was operated for 8 months, without a decrease in the single-pass removal efficiency, and withstood up to 15 days starvation periods with a marginal effect on its air refreshment capacity once the feeding of pollutants was restarted.
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    (33, 33) Morales-Vera, Rodrigo; Vásquez-Ibarra, Leonardo; Scott, Felipe; Puettmann, Maureen; Gustafson, Richard; 33
    Biomass appears to be one of the most prominent renewable resources for biofuels such as bioethanol, mainly due to its better environmental performance compared with fossil fuels. This study addresses a comprehensive environmental performance of bioethanol production, employing empirical data from hybrid poplar grown in the U.S. The study considers 1 MJ as a functional unit and employs a cradle-to-grave approach, which entails the feedstock and harvesting production of poplar, transport to a biorefinery, bioconversion of the biomass process, and fuel use. On average, bioconversion is the main contributor to environmental degradation in all the categories evaluated (77%). The second main contributor is either the feedstock and harvesting production of poplar (17%) or fuel use (6%), depending on the environmental category. Thus, focusing on only one category may induce a misinterpretation of the environmental performance of bioethanol production. Finally, environmental credits in the global warming potential (GWP) category were obtained from the carbon sequestered in the biomass during the growing period and from avoided fossil fuel emissions due to electricity production from a renewable source. This means that the net GWP of the life cycle of bioethanol from poplar biomass is slightly negative (?1.05 × 10?3 kg CO2-eq·MJ?1).
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    (33, 33) Yáñez, Luz; Rodríguez, Yadira; Scott, Felipe; Vergara-Fernández, Alberto; Muñoz, Raúl; 33
    Methylocystis parvus OBBP accumulates polyhydroxybutyrate (PHB) using methane as the sole carbon and energy source. In this work, the feasibility of producing (R)-3-hydroxybutyric acid (R3HBA) via intracellularly accumulated PHB through depolymerization (in-vivo) was investigated. Results showed that a PHB to R3HBA conversion of 77.2 ± 0.9% (R3HBA titer of 0.153 ± 0.002 g L-1) can be attained in a mineral medium containing 1 g L-1 KNO3 at 30 °C with shaking at 200 rpm and a constant pH of 11 for 72 h. Nitrogen deprivation and neutral or acidic pHs strongly reduced the excreted R3HBA concentration. Reduced oxygen availability negatively affected the R3HBA yield, which decreased to 73.6 ± 4.9% (titer of 0.139 ± 0.01 g L-1) under microaerobic conditions. Likewise, the presence of increasing concentrations of R3HBA in the medium before the onset of PHB depolymerization reduced the initial R3HBA release rate and R3HBA yield.
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    (33, 33) Moreno-Casas, Patricio A.; Scott, Felipe; Delpiano, Jose; Abell, Jose A.; Caicedo, Francisco; Muñoz, Raul; Vergara-Fernández, Alberto; 33
    The gas?liquid mass transfer coefficient is a key parameter to the design and operation of biotrickling filters that governs the transport rate of contaminants and oxygen from the gas phase to the liquid phase, where pollutant biodegradation occurs. Mass transfer coefficients are typically estimated via experimental procedures to produce empirical correlations, which are only valid for the bioreactor configuration and range of operational conditions under investigation. In this work, a new method for the estimation of the gas?liquid mass transfer coefficient in biotrickling filters is presented. This novel methodology couples a realistic description of the packing media (polyurethane foam without a biofilm) obtained using microtomography with computational fluid dynamics. The two-dimensional analysis reported in this study allowed capturing the mechanisms of the complex processes involved in the creeping porous air and water flow in the presence of capillary effects in biotrickling filters. Model predictions matched the experimental mass transfer coefficients (±30%) under a wide range of operational conditions.
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    (33, 33) España, Francisco; Scott, Felipe; 33
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    (33, 33) San Martín-Davison, Jessica; Lebrero, Raquel; Vergara-Ojeda, Christian; Scott, Felipe; Huiliñir, Cesar; Vergara-Fernández, Alberto; 33
    Background: Naphthalene is a polycyclic aromatic hydrocarbon, highly dangerous for human health. It is produced as a byproduct of incomplete combustion of organic material and is frequently present in the air. Biofilters offer an effective alternative for its treatment. The aim of this work was to study the treatment of naphthalene vapors through biofiltration using two biofilters: one inoculated with a consortium composed of Fusarium solani and Rhodococcus erythropolis (BF1), and the other inoculated with a consortium of microbial isolates obtained from a previous biofilter eliminating naphthalene vapors. Results: The results demonstrate that inoculating a biofilter with a reconstructed consortium of microbial isolates from a naphthalene vapor-eliminating biofilter allowed a reduction of the startup time from 35 to 5 days, while maintaining a consistent removal capacity (6 g m?3 h?1, equivalent to 80% removal efficiency). It was also observed that the biofilter inoculated with the reconstructed consortium exhibited comparable robustness to a biofilter previously operated for 4 months with naphthalene, with a maximum removal capacity of 14 g m?3 h?1 for a naphthalene inlet load of 17 g m?3 h?1. The study of microbial communities indicates an increase in the bacterial variability, while fungal variability remains low, with Fusarium solani being predominant at 97%. Conclusions: Results obtained during the startup of both biofilters and by challenging biofilters to increasing naphthalene concentrations or decreasing empty bed residence time showed that startup time can be reduced sevenfold by selecting the microbial consortium. An equivalent performance, in the long run, was achieved for both biofilters.
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    (33, 33) González, Ernesto; Zuleta, Camila; Zamora, Guiselle; Maturana, Nataly; Ponce, Belén; Rivero, María Virginia; Rodríguez, Alberto; Soto, Juan Pablo; Scott, Felipe; Díaz-Barrera, Álvaro; 33
    Acidiphilium cryptum is an acidophilic, heterotrophic, and metallotolerant bacteria able to use dissolved oxygen or Fe(III) as an electron sink. The ability of this extremophile to accumulate poly(3-hydroxybutyrate) (PHB) and secrete extracellular polymeric substances (EPS) has also been reported. Hence, the aim of this work is to characterize the production of PHB and EPS by the wild strain DSM2389 using glycerol in shaken flasks and bioreactor. Results showed that maximum PHB accumulation (37–42% w/w) was obtained using glycerol concentrations of 9 and 15 g L?1, where maximum dry cell weight titers reached 3.6 and 3.9 g L?1, respectively. The culture in the bioreactor showed that PHB accumulation takes place under oxygen limitation, while the redox potential of the culture medium could be used for online monitoring of the PHB production. Recovered EPS was analyzed by Fourier-transform infrared spectroscopy and subjected to gas chromatography—mass spectrometry after cleavage and derivatization steps. These analyses showed the presence of sugars which were identified as mannose, rhamnose and glucose, in a proportion near to 3.2:2.3:1, respectively. Since glycerol had not been used in previous works, these findings suggest the potential of A. cryptum to produce biopolymers from this compound at a large scale with a low risk of microbial contamination due to the low pH of the fermentation process.
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    (33, 33) Nolasco, Eduardo; Vassiliadis, Vassilios S.; Kähm, Walter; Adloor, Sai Darshan; Ismaili, Riham Al; Conejeros, Raúl; Espaas, Thomas; Gangadharan, Nishanthi; Mappas, Vasileios; Scott, Felipe; Zhang, Qianyue; 33
    Roger W.H. Sargent (1926–2018) was an unprecedented pioneer who foresaw the role that mathematical and computational tools would have in chemical engineering. His visionary work created the multidisciplinary field of Process Systems Engineering (PSE), a field that acts as a central hub influencing all subfields of chemical engineering. His particular interest in optimal control applied to industrial processes led him to develop numerical techniques to solve large-scale optimal control problems. In this work, a brief overview of the theory of optimal control is offered, spanning from its roots in calculus of variations to Pontryagin's maximum principle and some of its extensions. Furthermore, important contributions made by Sargent and his students are presented. Selected applications currently found in literature are presented as well–ranging from classical chemical engineering systems to bioprocesses. Some future perspectives of the field are also presented in the concluding section.
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    (33, 33) Silva, Pablo; Scott, Felipe; Adloor, Sai Darshan; Vassiliadis, Vassilios S.; Illanes, Andrés; Wilson, Lorena; Conejeros, Raúl; 33
    Enzyme inactivation significantly impacts reactor performance by reducing substrate conversion and product quality. This study, with its focus on optimizing the economic benefits of a novel two-step biocatalytic system, aims to control biocatalyst replacement intervals and operational conditions, thereby enhancing the economic viability of biocatalytic processes. The results demonstrate that optimal control strategies can be effectively implemented for Continuous Stirred Tank Reactors (CSTRs) and Packed Bed Reactors (PBRs). Moreover, PBRs show distinct advantages due to their enhanced capacity to meet demand, primarily resulting from differences in mixing patterns and the extended contact time between reactants and the biocatalyst. An essential contribution of this work is the detailed spatial analysis of temperature distribution within the PBR, an innovative approach to studying multienzyme systems. Considering a 16-week time horizon, the application of the proposed methodology resulted in a total of 3 catalyst changeovers for the CSTR configuration, and one for the PBR, achieving 80% of the total seasonal demand. Furthermore, the development of a comprehensive model that integrates two-stage enzyme inactivation, diffusional limitations, and Michaelis–Menten kinetics for both enzymes provides a thorough understanding and valuable insights into determining optimal biocatalyst replacement times. This approach advances the design and operation of biocatalytic processes for improved economic performance.
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    Acidophilic heterotrophs: basic aspects and technological applications
    González, Ernesto; Vera, Fernando; Scott, Felipe; Guerrero, Cecilia; Bolívar, Juan M.; Aroca, Germán; Muñoz, Jesús Ángel; Ladero, Miguel; Santos, Victoria E.
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    Beyond Intracellular Accumulation of Polyhydroxyalkanoates: Chiral Hydroxyalkanoic Acids and Polymer Secretion
    Yañez, Luz; Conejeros, Raúl; Vergara-Fernández, Alberto; Scott, Felipe
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    Biodegradation of 2,5-dimethylpyrazine in gas and liquid phase by the fungus Fusarium solani
    Araya, Blanca; Diaz, Camilo; Martín, Jessica San; Vergara-Fernández, Alberto; Aroca, Germán; Scott, Felipe
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    Biofiltration of volatile organic compounds and polycyclic aromatic hydrocarbons
    (Elsevier) Vergara-Fernández, Alberto; Scott, Felipe; Moreno-Casas, Patricio
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    Computational tomography and CFD simulation of a biofilter treating a toluene, formaldehyde and benzo[?]pyrene vapor mixture.
    Moreno-Casas, Patricio A.; Scott, Felipe; Delpiano, José; Vergara-Fernández, Alberto
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    A convenient method to validate the gas flow of a CFD-CT simulation applied on a packed bed used in gas biofiltration through residence time distributions
    Carreño-López, Felipe; Moreno-Casas, Patricio A.; Scott, Felipe; Iza, Jon; Sierra-Pallares, José; Muñoz, Raúl; Vergara-Fernández, Alberto