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•Pre-treatments modified the structure and composition of Agave durangensis leaves.•Pre-treated Agave durangensis leaves have better enzymatic digestibility.•Ultrasound pre-treatment ...increases the production of hydrolytic enzymes.
Approximately 1 million tons of agave plants are processed annually by the Mexican tequila and mezcal industry, generating vast amounts of agroindustrial solid waste. This type of lignocellulosic biomass is considered to be agroindustrial residue, which can be used to produce enzymes, giving it added value. However, the structure of lignocellulosic biomass makes it highly recalcitrant, and results in relatively low yield when used in its native form. The aim of this study was to investigate an effective pre-treatment method for the production of commercially important hydrolytic enzymes. In this work, the physical and chemical modification of Agave durangensis leaves was analysed using ultrasound and high temperature as pre-treatments, and production of enzymes was evaluated. The pre-treatments resulted in modification of the lignocellulosic structure and composition; the ultrasound pre-treatment improved the production of inulinase by 4 U/mg and cellulase by 0.297 U/mg, and thermal pre-treatment improved β-fructofuranosidase by 30 U/mg.
•Slurry-phase hydrocracking kinetics of a heavy oil in a batch reactor was determined.•High residue conversion was attained, even at low reaction time.•High selectivity toward Naphtha was ...obtained.•Slurry catalyst resists coke formation.
The kinetics of slurry phase heavy oil hydrocracking with nickel nanoparticles dispersed in PEG300 as the slurry phase catalyst was investigated. Colloidal metal nanoparticles were synthesized using a chemical reduction method. Catalytic evaluations were performed in a batch reactor with 7.0 MPa H2 and varying temperatures (310–370 °C) and reaction times (4–72 h). A five-lump kinetic model was used to obtain kinetic parameters using the R software with the Levenberg-Marquardt nonlinear least-squares algorithm. The order of the residue hydrocracking reaction rate equation was 2.5. The activation energies were determined, and the calculated product compositions were in agreement with the experimental values (<5%). The residue exhibited high selectivity towards naphtha. High residue conversion was accomplished, even at low reaction times.
A novel process to obtain H2 from flat plate aluminum corrosion in aqueous acid solutions is described. A modified traditional shrinking core model has been developed to analyze kinetics behavior by ...including the effect of growing and textural changes of hydroxide layer during reaction. Modified model is fitted to experimental data. Initial diffusion coefficient, magnitude of the change in its value and the ratio of volume of the produced shell to volume of consumed core during reaction were determined by parameters obtained from fitting the proposed model to experimental data.
•Kinetics of flat plate aluminum corrosion in aqueous acid solutions was studied.•Modified traditional shrinking core model has been developed.•It was found that diffusion of ion species/water molecules controls rate of reaction.•Overall diffusion coefficient is not constant over time.•Thickness of the shell increase at lower HCl concentrations.
The catabolism of tryptophan has gained great importance in recent years due to the fact that the metabolites produced during this process, with neuroactive and redox properties, are involved in ...physiological and pathological events. One of these metabolites is kynurenic acid (KYNA), which is considered as a neuromodulator since it can interact with NMDA, nicotinic, and GPR35 receptors among others, modulating the release of neurotransmitters as glutamate, dopamine, and acetylcholine. Kynureninate production is attributed to kynurenine aminotransferases. However, in some physiological and pathological conditions, its high production cannot be explained just with kynurenine aminotransferases. This review focuses on the alternative mechanism whereby KYNA can be produced, either from D-amino acids or by means of other enzymes as D-amino acid oxidase or by the participation of free radicals. It is important to mention that an increase in KYNA levels in processes as brain development, aging, neurodegenerative diseases, and psychiatric disorders, which share common factors as oxidative stress, inflammation, immune response activation, and participation of gut microbiota that can also be related with the alternative routes of KYNA production, has been observed.
Feasibility analysis of methane reforming by hydrogen sulfide for hydrogen production from technical and economical viewpoints was made. An improved Hydrogen Sulfide Methane Reformation (H2SMR) ...process flowsheet was proposed in order to compare its production costs with those of Steam Methane Reformation (SMR) conventional process. Major findings were: high production of hydrogen, a partial self-sustainability process since some of the hydrogen produced could be used as an energy source, no greenhouse gases generated, common sizes of main equipment for a typical H2 production and the possibility of eliminating Claus plants. Aspen Plus® V8.4 simulation software was used. Results showed H2SMR is a more economical source of H2 production than SMR conventional process, with an estimated cost of 1.41 $/kg.
•A H2SMR process flowsheet was proposed to analyze its techno-economic feasibility.•Aspen Plus simulator was used in order to achieve a competitive technical H2SMR process.•H2SMR partial self-sustainability process was proposed to reduce energy cost.•Results demonstrate H2SMR process could be competitive and financially viable option.
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