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The use of lignocellulosic residues as feedstocks for biofuels production represents an economic and ecofriendly option, since they are generated as byproducts or wastes from different industrial areas. Nevertheless, a pretreatment method aimed at eliminating the lignin content of these residues must be performed. This is required in order to increase cellulose bioavailability, which favors the production of reducing sugars through microbial or enzymatic attack. Some performed pretreatments can be classified as physical, chemical, and physicochemical methods. Although such methods are the most used pretreatments, they are expensive and generate or make use of harmful compounds. Biological methods, by the action of microorganisms or their enzymes for lignin content reduction, may be regarded as an alternative, being cheaper and more friendly to the environment than the aforementioned methods. However, until now, biological pretreatments have not shown the same yield as the previously mentioned methods in both sugar recovery and biofuel production. In that sense, the aim of this work is to review the efficiency of these methods, with the goal of clarifying their advantages and disadvantages for improvement of biofuel production. [ABSTRACT FROM AUTHOR]

Modeling of the bioleaching process applied to the system silver‐manganese (Ag‐Mn) was carried out. The two‐moving‐fronts model was used to describe the main stages of the process. Bioleaching involves a catalytic process carried out by bacteria to dissolve the mineral ores. Initially, the bacteria interact with the mineral to dissolve manganese, leading to the precipitation of silver. The Ag‐Mn compound is dissolved by the bacteria in two stages. First, the bacteria dissolve the manganese and form a biofilm composed mostly of exopolysaccharides. In the second stage, the biofilm is consumed by the bacteria, ending up in dissolved manganese and silver precipitation. At 48 h, the viscosity of the pulp reaches a maximum attributed to the maximum concentration of extracellular polysaccharides in the medium. Predictions describe the basic issues of the bioleaching process in this system. [ABSTRACT FROM AUTHOR]

The objective of this work was to obtain glass-ceramics from stable glasses, with a composition of barium, lead, and potassium titanate phases, for use as semiconductors. For this purpose, the glass-ceramic technique was used to control crystal growth and obtain a fine-grained microstructure. Various glasses containing K2O, PbO, BaO, Al2O3, B2O3, and TiO2 were prepared using a melt-quenching method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed a single amorphous phase of all samples. Infrared spectra confirmed the presence of B-O bonds stretching vibrations of (B3O6)3− boroxol rings and BO3 triangles, as well as Ti-O stretching vibrations of (TiO6/2) and (AlO6/2) octahedral units. Thermal analyses confirmed the presence of one or more crystallization peaks in the range of 700 to 744 °C. On this base, they were heat-treated to promote crystal growth. XRD and SEM detected Ba4Ti12O27, Ti7O13, and BaTiO3 phases, homogeneously distributed throughout the material with fine crystallite size. In addition, crystallized glasses' (glass-ceramics) properties were determined; the density values were 2.8–3.55 g/cm3; the chemical resistance to acidic and basic media was low; and the band-gap values were in the range of 2.88 to 3.05 eV. These results suggest that crystallized glasses may have application in photocatalysis. [ABSTRACT FROM AUTHOR]

Fermentation with filamentous fungi in a bioreactor is a complex dynamic process that is affected by flow conditions and the evolution of the rheological properties of the medium. These properties are mainly affected by the biomass concentration and the morphology of the fungus. In this work, the rheological properties of a fermentation with the fungus Beauveria bassiana under different hydrodynamic conditions were studied and the rheological behavior of this broth was simulated through a mixture of carboxymethyl cellulose sodium and cellulose fibers (CMCNa-SF). The bioreactor was a 10 L CSTR tank operated at different stir velocities. Rheological results were similar at 100 and 300 rpm for both systems. However, there was a significant increase in the viscosity accompanied by a change in the consistence index, calculated according to the power law model, for both systems at 800 rpm. The systems exhibited shear-thinning behavior at all stir velocities, which was determined with the power law model. The mixing time was observed to increase as the cellulose content in the system increased and, consequently, the efficiency of mixing diminished. These results are thought to be due to the rheological and morphological similarities of the two fungal systems. These results will help in the optimization of scale-up production of these fungi.