Abstract in English:Nowadays the discovery of new compounds from microorganisms has substantially decreased. Genomic studies have shown that certain genes are not expressed under standard laboratory conditions. In order to overcome this problem, several methods including microorganism co-culture have been developed. The aim of this work was to select binary co-cultures of marine-derived microorganisms to pursue further chemical studies. From 15 microorganisms, 151 interactions assays in solid media were performed using two different methodologies: distance assays and contact assays that allowed to distinguish between interactions due to diffusible compounds or due to cell-cell contact. For distance assays, the metabolic production changes were evaluated using 3 zones: two corresponding to each microorganism colony, and a third zone corresponding to the interaction zone. This division zone strategy allowed to assess the diffusion compounds gradient, and to suggest the producer microorganism of the induced compounds. The metabolic production of the co-cultures was evaluated using HPLC-DAD and NMR. Seven co-cultures were identified to be able to induce changes in the metabolic production. Remarkably, the co-culture between the fungus Purpureocillium sp. PNM-67 and the bacteria Rhodococcus sp. RKHC-26 or Gordonia sp. PNM-25 induce production of a red dye in the fungus. These are the first successful examples of interaction between a fungus and a mycolic acid-containing bacteria.
Abstract in Portuguese:Technologies developed in the last decade have made viable the use of lignocellulosic materials for the production of ethanol. However, to improve the fermentative yield some improvements are necessary, among them the search for new microorganisms capable of fermenting sugars with five carbons. Thus, the present research aimed to determine the best pH and temperature for Pichia membranifaciens LJ04 in synthetic medium containing pentose, aiming at the biotechnological production of ethanol from hemicellulosic hydrolysate. The experimental design was completely randomized in Split-Split-Plot, with 3 replicates. The main treatments were pHs (3.5, 4.0 and 4.5), the secondary were temperatures (32 ºC, 37 ºC and 40 ºC) and the tertiary were fermentation periods (0, 6, 12 and 24 hours). It was determined in this study that the ideal conditions were temperature of 32 ºC and pH 4.0-4.5. With these conditions there was higher xylose consumption, high ethanol production, low production of secondary compounds and high rates of cell viability during fermentation.
Abstract in English:The optimized analytical methodology described herein is based on an ion exchange column and an H3PO4 solution (pH 2.24) as the mobile phase, with a flow rate of 0.4 mL min-1 and refractive index detection (RID). On applying the methodology, it was possible to identify 7 products obtained from the oxidation of glycerol with an analysis time of 27 min. The developed method was validated through the evaluation of a series of analytical parameters. The results obtained were evaluated considering the peak area and peak height. The analytical curves showed a correlation coefficient of ≥ 0.986. The coefficient of variation values obtained were ≤ 3.60% for instrumental precision, ≤ 19.36% for intermediate precision in LOQ (1.25 µg mL-1) and ≤ 17.93% for repeatability in LOQ (1.25 µg mL-1) and different days. The limit of quantification established for all compounds was 1.25 µg mL-1 obtained through the parameters of the analytical curve. The accuracy of the method showed recovery values of 85.6 to 112.3% for real fortified sample at 3 concentration levels. Two different samples of glycerol oxidation products were applied to the validated methodology; one obtained from AuNP/SiO2 as catalyst (conversion of 62.42%), and other using AuNP/MWCNT (conversion of 89.5%).
Abstract in Portuguese:Extracts of black mulberry leaves present phytochemicals such as phenolic compounds and minerals. These substances have been studied because they show several health benefits. In this work we report the influence of drying temperature, infusion temperature and extraction time by means of factorial design monitoring the total phenolic content (CFT) of aqueous extracts of leaves of Morus nigra L. The concentrations of CFT, flavonoids, flavonols and antioxidant activity of the extracts were determined by spectrophotometry. The identification and quantification of phenolic compounds were performed by LC-ESI-MS / MS. The determination of the mineral concentration in the black mulberry leaves was performed by ICP-MS. The Pareto and surface response graphs suggested that the most efficient extractions occurred for leaves drying at lower temperatures and using higher infusion temperatures, extraction time did not show significant influence. The extracts presented concentration of CFT from 16.96 ± 0.15 to 5.73 ± 0.33 mg GAE g-1. The analyzes by LC-ESI-MS / MS allowed to identify phenolic substances not yet reported in the literature to date. In addition 10 mineral elements were determined in the black mulberry leaves at mg kg-1 concentrations range.
Abstract in English:Keggin heteropolyacids (HPW) supported on niobia have been considered for both homogeneous and heterogeneous catalysis due to its special features, like the strong Brönsted acidity, low volatility, high activity and high selectivity for various reactions in comparison with mineral acids. Literature reports many different preparation methods for these catalysts through the addition of HPW solutions, in either water or acid, over niobia under stirring. However not much is known about the way how HPW interacts with the support, neither how the temperature influences this interaction. In order to contribute to expand the knowledge on this field we report here a new way of preparing HPW supported catalysts over niobia calcined at 500 and 600 ºC, followed by a theoretical study meant to check the influence of the temperature increase on the adsorption behavior of the catalysts over the support. Our proposed method showed to be an efficient alternative for impregnation of HPW over niobia, while the theoretical results suggest that pseudohexagonal and orthorhombic are the most likely crystalline forms for these catalysts.
Abstract in English:In this work, a series of PhnSnCl4-n (n = 1, 2, 3, and 4) based catalysts were prepared by incipient wetness impregnation using activated carbon (AC) as support and triphenyltin chloride (Ph3ClSn) and tin(IV) chloride (SnCl4) as Sn precursors. The obtained catalysts were systematically characterized by X-ray diffraction (XRD), N2 physisorption, Scanning electron microscope (SEM), Thermogravimetric analysis (TG-DTG), and Inductively coupled plasma (ICP) analytical techniques. The catalytic performance of the prepared PhnSnCl4-n samples was evaluated in the acetylene hydrochlorination reaction. When a gas hourly space velocity (GHSV, C2H2 based) and a reaction temperature of 30 h-1 and 200 ºC, respectively were used for the reaction performed over the 12% (1.0Ph3ClSn+3.5SnCl4)/AC-200 catalyst, an acetylene conversion of 98.0% with a selectivity to vinyl chloride of 98.5% were obtained. These results demonstrated that PhnSnCl4-n can effectively improve the catalytic activity and prolong the lifetime of SnCl4/AC catalysts. Moreover, by comparing with HgCl2/AC, PhnSnCl4-n-based catalysts exhibit much enhanced catalytic activity in the hydrochlorination of acetylene. It is assumed that the outstanding activity is due to trichlorophenylstannane (PhCl3Sn) active sites, resulted from the organotin redistribution reaction between Ph3ClSn and SnCl4. In addition, such sites also improved the SnCl4/AC catalyst stability during the reaction.
Abstract in Portuguese:This work aims to determine the kinetic parameters of the thermal decomposition of a lubricating grease based on perfluoropolyether (PFPE) and the computational simulation of this decomposition. The determination of kinetic parameters of thermal decomposition was done by thermal analysis using thermogravimetry (TG) at different heating rates (β) of 10, 15 and 20 ºC min-1. With the TG curves obtained, the kinetic parameters were determined by the kinetics methods of Goldfarb et al. and Duvvuri et al., Flynn-Wall-Ozawa and Kissinger. The activation energy of the thermal decomposition of the PFPE grease in the kinect models ranged from 63.54 to 112.3 kJ mol-1. The results of the thermogravimetry indicated that the PFPE grease is thermally stable up to 300 ºC. A simulation of the thermal decomposition of the PFPE oil base was carried out by molecular dynamics simulation, using LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) in a temperature range of 0 to 3500 K during 50 ps. The value of the activation energy in the simulation was 92 kJ mol-1. The results show that PFPE oil base and PFPE lubricant grease can be used in high-temperature applications.
Abstract in English:The enzymatic processes are increasingly highlights, especially in the synthesis of chemical products with high added value. The enzyme immobilization can improve industrial biocatalytic processes. The immobilization of enzymes provides the production of efficient, stable biocatalysts, possibility of reuse and easy purification of the products, when compared to the free enzymes. There is a growing research for more efficient methods of enzyme immobilization. In this context, the choice of support and immobilization strategy can significantly improve the final enzymatic properties. In this review paper, we aimed to discuss the versatility of biocatalysts immobilized enzymes design, focusing on the opportunities and disadvantages for each method presented. They discussed the recent development of enzyme immobilization methods and applications relating the final properties of the produced biocatalysts with the desired goals.
Abstract in English:The biotransformation reactions are used as a successful alternative to derivatization by the traditional chemistry because they conduct to uncommon reactions, which would hardly be carried out by chemical synthesis. A wide diversity of compounds may be metabolized by fungi, leading to chemical derivatives through selective reactions that work under ecofriendly conditions. Endophytic fungi live in symbiosis with health tissues of plants. The employment of endophytic fungi as enzymatic sources to biotransformation reactions is very promising since these microorganisms came from uncommon and underexplored habitat. The environmental conditions directly influence the composition of the endophytic microbiota and its genetic expression, which could change also the production of the enzymes. The extraordinary richness of the Brazilian biodiversity is a key factor in the diversification of the endophytic community. The present review presents a mapping of the biotransformation reactions catalyzed by Brazilian endophytic fungi. Our findings contribute both to the appreciation of these fungi in the chemical derivatization and for the preservation of the Brazilian species.
Abstract in English:Controllable geometry silicon surfaces with superhydrophobicity are difficult to be fabricated without photolithography techniques. Superhydrophobic silicon surfaces with water contact angle larger than 150º and sliding angle less than 10º have been successfully fabricated by electrochemical etching strategy. Squarelike hole arrays with controllable geometries, especially ole width and depth were formed on silicon. Compared with the chemical composition, the obvious change of the hole size and surface roughness with etching time was actually the intrinsic factors for wetting regulation. The superhydrophobic silicon exhibited good stability even after storage in air and oil for 2 months. Moreover, the relatively stable superhydrophobic silicon exhibited good self-cleaning and water-proofing properties in air and oil.
Abstract in English:For this work, a hydroalcoholic extract was prepared from the aerial parts of the Malvaviscus arboreus (Malvaceae) species, popularly known as hibisco-colibri in Brazil; and then, investigated by infrared and NMR spectroscopy. A class of special metabolites containing a porphyrin skeleton and pyrrole units was determined by typical absorption spectra, mainly 1H and 13C NMR, thus indicating the capability of showing anti-corrosion effect. Therefore, the M. arboreus extract was examined as a corrosion inhibitor for AISI 1020 carbon steel in H2SO4 1 mol L-1, using a mass loss (gravimetric) technique. Results showed good corrosion inhibition efficiency, at both time and temperature variation. The maximum efficiency observed at 500 ppm was 97.5%, at 3 h, 24 h and 48 h. The surface morphology was analyzed by scanning electron microscopy (SEM), through which a higher homogeneity was observed in the presence of the M. arboreus extract. The hydroalcoholic extract of hibisco-colibri can be considered an efficient green agent for preventing corrosion.
Abstract in English:Considering the importance of non-school educational spaces to diffusing scientific knowledge, as well as arguments for the inclusion of such spaces into initial teacher education, this study presents four strategies to make them practice field institutions in chemistry teacher licensure programs. Assuming that the modalities of the educational phenomenon can be divided into unsystematic and systematized - whether they be school or non-school forms -, the strategies were named as follows: a) Learning (from) the concept of systematicity; b) The school learns from the museum (or the museum learns from the school); c) The museum in the school; and d) Systematizing non-systematic school education. After describing the strategies, we analyzed reports of chemistry teachers in training. These reports included reflections on the social importance of school and chemical knowledge, and they overcame the technical and practical rationalities by incorporating principles of critical rationality.
Abstract in English:The importance of hybrid atomic orbitals, both historically and mathematically, is reviewed. Our new analysis of the original derivation of the sp3, sp2, sp model reveals serious errors. Based on a critical survey of the literature, we submit six formal criteria that deprecate the use of hybrid orbitals in a pedagogical context. A sound mathematical basis of sp3 and sp2 formulae does not exist; hybrid atomic orbitals have hence no legitimate role in the teaching of organic chemistry.
Abstract in English:The importance of hybrid atomic orbitals, in both general and organic chemistry, is reviewed. Every contemporary textbook of organic chemistry introduces the directed-valence (e.g. sp3, sp2, sp) model, but the suitability of these hybrid orbitals for use in the teaching of molecular structure has been increasingly questioned. Based on a critical survey of the literature, we submit seven practical criteria that deprecate the use of hybrid orbitals in a pedagogical context. We suggest how the teaching of organic chemistry without hybrid orbitals will provide students with an enhanced education.