Sandy Luz Ovando-Chacon

This study reports for the first time the isolation, identification and characterization of lipase-producing thermophilic strain from the geothermal water of the El Chichón volcano crater lake. Two strains were identified by 16S rRNA sequencing as Geobacillus jurassicus CHI₂ and Geobacillus stearothermophilus CHI₁. Results showed that G. jurassicus CHI₂ is Gram-positive, able to ferment maltose, fructose and sucrose and to hydrolyze starch and casein; while G. stearothermophilus CHI₁ showed to be Gram-variable, able to ferment maltose and fructose and to hydrolyze starch. Colonies of both strains presented irregular shape, umbilicated elevation of gummy texture and cells presented flagellar movement to survive in fluids with high temperature and mass gradients due to complex phenomena of heat and mass transfer present in the geothermal fluids. Lipase production for G. stearothermophilus CHI₁ was also evaluated. It was found that this strain possesses a growth associated with extracellular lipase production with a high activity of 143 U/mL at 8.3 h of incubation time, superior to the activities reported for other microorganisms of genus Geobacillus; for this reason, it can be said that the thermal flow of the El Chichón volcano crater lake can be a useful source of lipase-producing thermophilic bacteria.

Heat exchangers play an important role in different industrial processes; therefore, it is important to characterize these devices to improve their efficiency by guaranteeing the efficient use of energy. In this study, we carry out a numerical analysis of flow dynamics, heat transfer, and entropy generation inside a heat exchanger; an aqueous medium used for oil extraction flows through the exchanger. Hot water flows on the shell side; nanoparticles have been added to the water in order to improve heat transfer toward the cold aqueous medium flowing on the tube side. The aqueous medium must reach a certain temperature in order to obtain its oil extraction properties. The analysis is performed for different Richardson numbers (Ri = 0.1–10), nanofluid volume fractions (φ = 0.00–0.06), and heat exchanger heights (H = 0.6–1.0). Results are presented in terms of Nusselt number, total entropy generation, Bejan number, and performance evaluation criterion. Results showed that heat exchanger performance increases with the increase in Ri when Ri > 1 and when reducing H.

En el presente trabajo se analizó la composición bromatológica de la semilla de cacaté (Oecopetalum mexicanum) y se optimizó el proceso de extracción acuoso enzimático del aceite. Los preparados enzimáticos Crystalzyme Cran y Cellulase fueron evaluados para determinar su influencia sobre los rendimientos de extracción del aceite de O. mexicanum. La parte experimental se desarrolló en dos etapas, en la primera se evaluó el efecto de las variables tipo de enzima, concentración de enzima, tamaño de partícula y tiempo de incubación mediante un diseño experimental L8 tipo Taguchi, la segunda etapa consistió en optimizar aquellas variables que influyeron sobre el rendimiento de aceite, a través de un diseño Box-Benhken. Los resultados del análisis bromatológico muestran que la semilla de cacaté contiene 39.25±0.33% de aceite.

A numerical investigation of laminar flow in a two-dimensional, Cartesian flow that exits from a short channel with a backward-facing step is carried out in this work for the Reynolds number range of 0.00054 < Re < 54. We studied the steady state fluid dynamics, phase change and heat transfer of the flow. We analyzed the flow behavior occurring for different outflow velocities and three different configuration of the step. The incompressible working fluid was glass. The temperature, streamline, phase change and pressure fields are obtained and analyzed as a function of position. In order to obtain a better understanding of the step angle influence on the fluid dynamics, we obtained the heat transfer flux rates and the axial velocity profiles.