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This work reports the dielectric behavior of the biopolymer ethyl cellulose (EC) observed from transient currents experiments under the action of a direct current (DC) electric field (~107 V/m) under vacuum conditions. The viscoelastic response of the EC was evaluated using dynamic mechanical analysis (DMA), observing a mechanical relaxation related to glass transition of around ~402 K. Furthermore, we propose a mathematical framework that describes the transient current in EC using a fractional differential equation, whose solution involves the Mittag–Leffler function. The fractional order, between 0 and 1, is related to the energy dissipation rate and the molecular mobility of the polymer. Subsequently, the conduction mechanisms are considered, on the one hand, the phenomena that occur through the polymer–electrode interface and, on the other hand, those which manifest themselves in the bulk material. Finally, alternating current (AC) conductivity measurements above the glass transition temperature (~402 K) and in a frequency domain from 20 Hz to 2 MHz were carried out, observing electrical conduction described by the segmental movements of the polymeric chains. Its electrical properties also position EC as a potential candidate for electrical, electronics, and mechatronics applications. [ABSTRACT FROM AUTHOR]

Dielectric and thermal properties of polyvinyl butyral (PVB) were studied in this work, using dynamic electrical analysis (DEA) at frequencies from 100 Hz to 1 MHz and temperatures from 293 K to 473 K. Two electrical relaxation processes were investigated: glass transition and interfacial polarization. Above the glass transition temperature (~343 K), interfacial polarization dominates conductive behavior in polyvinyl butyral. The framework of the complex electric modulus was used to obtain information about interfacial polarization. The viscoelastic behavior was analyzed through dynamic mechanical analysis (DMA), where only the mechanical manifestation of the glass transition is observed. The experimental results from dielectric measurements were analyzed with fractional calculus, using a fractional Debye model with one cap-resistor. We were successful in applying the complex electric modulus because we had a good correlation between data and theoretical predictions. The fractional order derivative is an indicator of the energy dissipated in terms of molecular mobility, and the calculated values close to 1 suggest a conductive behavior at temperatures above the glass transition temperature of PVB. [ABSTRACT FROM AUTHOR]

Today, shape memory alloys (SMAs) have important applications in several fields of science and engineering. This work reports the thermomechanical behavior of NiTi SMA coil springs. The thermomechanical characterization is approached starting from mechanical loading–unloading tests under different electric current intensities, from 0 to 2.5 A. In addition, the material is studied using dynamic mechanical analysis (DMA), which is used to evaluate the complex elastic modulus E* = E′ − iE″, obtaining a viscoelastic response under isochronal conditions. This work further evaluates the damping capacity of NiTi SMA using tan δ, showing a maximum around 70 °C. These results are interpreted under the framework of fractional calculus, using the Fractional Zener Model (FZM). The fractional orders, between 0 and 1, reflect the atomic mobility of the NiTi SMA in the martensite (low-temperature) and austenite (high-temperature) phases. The present work compares the results obtained from using the FZM with a proposed phenomenological model, which requires few parameters for the description of the temperature-dependent storage modulus E′. [ABSTRACT FROM AUTHOR]

Fractional calculus models can potentially describe the viscoelastic phenomena in soft solids. Nevertheless, their successful application is limited. This paper explored the potential of using fractional calculus models to describe the viscoelastic properties of soft solids, focusing on methylcellulose aqueous systems. Methylcellulose is an important food additive, and it is known for its complex rheological behaviors, including thermogelation, which still puzzle rheologists. Through dynamic mechanical analysis and fractional rheology, we demonstrated that fractional calculus described the frequency- and temperature-dependent rheology of methylcellulose. This paper also showcased how including one springpot could potentially replace numerous spring-dashpot arrangements. Our findings using fractional calculus suggested that the thermogelation of methylcellulose involves the cooperative mobility of polymer chains and can be described as a process analogous to the glass transition in polymers. This study highlighted the power of combining fractional calculus and rheology to understand complex viscoelastic phenomena in soft solids. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Dried solid-state fermented solids (biocatalysts) produced by seven thermotolerant fungal strains were tested for lipase activity and stability in organic solvents. Two strains of Rhizopus sp. (19 and 43a) produced biocatalysts (L-19 and L-43a) that showed high lipase activities (74 and 72U/g of dry matter, respectively) comparable to Lipozyme® RM IM (118U/g DM). The use of the dipole moment of the organic solvents along with their classification based on the functional groups (non-polar, protic polar, aprotic polar) allowed the establishment of four different relative activity profiles for the seven biocatalysts evaluated. Compared to a biocatalyst not exposed to the organic solvent (100% relative activity), all biocatalysts showed a high relative activity (greater than 90%) in aprotic polar solvents (acetonitrile, acetone and ethyl acetate), whereas in protic polar solvents (ethanol and i-propanol) activity was reduced (lower than 40%). In addition, the incubation of biocatalysts L-19 and L-43a in i-amyl alcohol increased lipase activity in the synthesis of ethyl oleate 3.36 and 1.46 times, respectively. L-19 activity also increased after incubation in toluene (2.0 times), i-propanol (1.5 times) and acetonitrile (1.3 times) at temperatures from 30 to 50°C. The results suggest that these biocatalysts can be used for a broad range of lipase reactions. [Copyright &y& Elsevier]

Abstract: Albumins are highly conserved proteins that carry out a multitude of physiological functions and exhibit a broad range of catalytic activities. Moreover, amino acid sequence comparisons of the albumin multigene family indicate that albumins diverged from a common ancestor. Here we report that bovine serum albumin (BSA) can catalyze ester hydrolysis at high temperatures (as high as 160°C) well beyond the temperature limits reported for enzymatic catalysis, including for enzymes from known hyperthermophiles. Furthermore, BSA exhibited a ∼133-fold increase in its turnover number (k cat) toward p-nitrophenyl palmitate from 70 to 150°C. When BSA was incubated for 1h at 150°C in the presence of 25mM SDS, it retained complete esterase activity, indicating that a catalytically competent orientation of amino acid residues exists in the denatured or partially unfolded protein. However, esterase activity diminished to ∼50% upon disruption of the protein''s disulfide bridges and disappeared completely when BSA was digested by proteases. These results point to a new standard of robustness for biocatalytic activity at high temperatures. Catalytic activity and promiscuity at very high temperatures could have been advantageous to enzymes in primitive organisms evolving in hot environments, making BSA an intriguing model for early enzymes. [Copyright &y& Elsevier]

Barophilic growth of the hyperthermophilic methanarchaeon Methanocaldococcus jannaschii occurred when gas-substrate availability did not limit growth. In contrast, when growth was limited by gas transfer, no enhancement of growth was evident and a stress response was exhibited at both high and low pressure. A pressure-induced transcriptional response was evident, regardless of whether growth was enhanced by pressure. Potential high-pressure adaptation of a barophilic organism can thus occur at the transcriptional level, even though the cells are stressed by low substrate availability and do not exhibit accelerated growth. [ABSTRACT FROM AUTHOR]

Rett's syndrome (RS) is a pervasive neurodevelopmental disorder characterized by autistic behavior, stereotypic movements of hands, loss speech and communication, acquired microcephaly. The diagnosis of RS is mainly based on their clinical characteristics and evolution of the syndrome, there is no laboratory marker that facilitates diagnosis. RS patients often are confused with autism, although they differ in their evolution. We report a case of the RS diagnosed 3 years 9 months age where was found proliferation of harmful bacteria and yeast and high levels of neurotoxic metals. [ABSTRACT FROM AUTHOR]

Only a few halophilic archaea producing carboxylesterases have been reported. The limited research on biocatalytic characteristics of archaeal esterases is primarily due to their very low production in native organisms. A gene encoding carboxylesterase from Halobacterium salinarum NRC-1 was cloned and successfully expressed in Haloferax volcanii. The recombinant carboxylesterase (rHsEst) was purified by affinity chromatography with a yield of 81%, and its molecular weight was estimated by SDS-PAGE (33 kDa). The best kinetic parameters of rHsEst were achieved using p-nitrophenyl valerate as substrate (KM = 78 µM, kcat = 0.67 s−1). rHsEst exhibited great stability to most metal ions tested and some solvents (diethyl ether, n-hexane, n-heptane). Purified rHsEst was effectively immobilized using Celite 545. Esterase activities of rHsEst were confirmed by substrate specificity studies. The presence of a serine residue in rHsEst active site was revealed through inhibition with PMSF. The pH for optimal activity of free rHsEst was 8, while for immobilized rHsEst, maximal activity was at a pH range between 8 to 10. Immobilization of rHsEst increased its thermostability, halophilicity and protection against inhibitors such as EDTA, BME and PMSF. Remarkably, immobilized rHsEst was stable and active in NaCl concentrations as high as 5M. These biochemical characteristics of immobilized rHsEst reveal its potential as a biocatalyst for industrial applications. [ABSTRACT FROM AUTHOR]

This article focuses on studying the rheological behavior of isotropic and anisotropic magnetorheological elastomers (MREs), made of carbonyl iron microparticles dispersed into a silicone–rubber matrix by considering 20 and 30 wt % of microparticles. Sample sets were prepared for each composition, with and without the application of an external magnetic field. Experimental measurements of the material rheology behavior were carried out by a shear oscillatory rheometer at constant temperature, to determine both the shear storage modulus (G′) and shear loss modulus (G′′) for all characterized samples. Then, experimental data collected from the isotropic and the anisotropic material samples were used to plot the Cole-Cole diagrams to quantify the interfacial adhesion between carbonyl iron microparticles and the silicone-rubber matrix. Furthermore, the Fractional Zener Model (FZM) with two spring-pots in series is used for quantitative analysis of collected experimental data. [ABSTRACT FROM AUTHOR]

The marine bacterium Saccharophagus degradans was investigated for the synthesis of polyhydroxyalkanoates (PHAs), using glucose as the sole source of carbon in a two-step batch culture. In the first step the microorganism grew under nutrient balanced conditions; in the second step the cells were cultivated under limitation of nitrogen source. The biopolymer accumulated in S. degradans cells was detected by Nile red staining and FT-IR analysis. From GC–MS analysis, it was found that this strain produced a homopolymer of 3-hydroxybutyric acid. The cellular polymer concentration, its molecular mass, glass transition temperature, melting point and heat of fusion were 17.2 ± 2.7% of dry cell weight, 54.2 ± 0.6 kDa, 37.4 ± 6.0 °C, 165.6 ± 5.5 °C and 59.6 ± 2.2 J g−1, respectively. This work is the first report determining the capacity of S. degradans to synthesize PHAs. [ABSTRACT FROM AUTHOR]

• First report on the production and characterization of exopolysaccharide produced by Haloferax mucosum. • Haloferax mucosum showed high exopolysaccharide (EPS) production of 7.15 g/L. • EPS had a high molecular mass of 152. • EPS exhibited high emulsion stability to extreme conditions and with different nonpolar solvents. The physicochemical characterization and emulsifying functional properties of a novel exopolysaccharide (EPS) produced by haloarchaea Haloferax mucosum (DSM 27191) were investigated. This biopolymer has a high molecular weight of 152 kDa and important protein content of 10%. Different culture media compositions were investigated taking the ATCC 2185 medium as a base and supplementing with varying concentrations of yeast extract and glucose or sucrose as carbon sources to produce the EPS in a liquid medium. The highest EPS production (7.15 ± 0.44 g/L) was obtained at 96 h. EPS aqueous dispersions showed a non-Newtonian rheological behavior which was well fitted to the Cross equation. The EPS (at 0.32% w/w) was capable of stabilizing water-in-oil emulsions with different nonpolar solvents, including n -hexane, kerosene, chloroform, castor oil and mineral oil. EPS retained its emulsifying activity after to be incubated for one hour in a wide range of temperatures (25, 40, 70 and 100 °C), pH (4, 6.5, 7 and 12) and NaCl concentrations (0, 2.0 and 4.0 M). The viscoelastic behavior and stability of hexane-in-water emulsion were examined through oscillatory shear measurements. [ABSTRACT FROM AUTHOR]

Determination of optimum temperature in the (PFasa) cellulase production, by a strain of Aspergillus niger in solid fermentationis presented in this paper, using data from a previously proposed kinetic model. Dependence of the 16 kinetic parameters with temperature (in the range of 20 °C to 40 °C), was established. For µmax and xmax parameters, the adjustment was achieved using the Rosso and Ratkowsky models respectively. Cubic interpolation models was needed to adjust the rest of kinetic parameters. The dependence of the kinetic model parameters with temperature allowed the estimation of temperature and optimum fermentation time to maximize the productivity in the production of true protein and the activity of the three studied enzymes. As result, the optimum temperature rangeisbetween 30°C and 32°C. For the production of true protein and CMcasa, the optimum fermentation time is located within the19 and 22 hours respectively, but for the production of PFasa, is 33 hours. The protease activity presented several local maxima in terms of optimal temperatures ranging from 25 to 40 °C. Although the maximum activity levels are 64 UI/gdm, which, according to literature, is an intermediate value, the level of productivity of PFasa is the highest found (3.84 times superior to average activity), when compared with another 20 reports consulted since 2004. [ABSTRACT FROM AUTHOR]

In this work a kinetic model proposal is presented for describing cellulase production in a solid-state fermentation process of an Aspergillus niger strain. The validation of the model was carried out at five temperatures: 20, 25, 30, 35 and 40°C. In the validation the characteristic parameters of the model were identified using a dynamic data generated at constant temperature. The response variables described by the model are: concentration of biomass of fungus measured as true protein, total reducing sugars, crude fiber, FPase activity, CMCase activity and the activity of proteases in the medium. For parameters identification the process model was programmed in MATLAB. The results indicate that the model is perfectly capable describing the cellulase production kinetics under these conditions. The temperatures where cellulase production was higher were 30°C and 35°C. The experimental levels of FPase and CMCase are significant because maxim values of FPase of 60 UI gDW-1 and of CMCase of 50 UI gDW-1 are reached in a fermentation time ranging from 24 to 30 hours. The identified parameters are strongly associated to temperature. [ABSTRACT FROM AUTHOR]

The aim of this article focuses on identifying how the addition of iron micro- and nanoparticles influences the physical properties of magnetorheological composite materials developed with a polydimethylsiloxane (PDMS) matrix with different contents of silicone oil used as additive. A number of characterization techniques have been performed in order to fully characterize the samples, such as cyclic and uniaxial extension, rheology, swelling, Vibrating sample magnetometer (VSM), X-ray Diffraction (XRD), Scanning electron microscopy (SEM), Fourier-Transform Infrared (FTIR), X-ray photoelectronic spectroscopy (XPS) and Thermogravimetric analysis (TGA). The comparison between two matrices with different shore hardnesses and their mechanical and chemical properties are elucidated by swelling and tensile tests. In fact, swelling tests showed that higher crosslink density leads to increasing elongation at break and tensile strength values for the composite materials. The best mechanical performance in the magnetorheological material was observed for those samples manufactured using a higher silicone oil content in a hard polymeric matrix. Furthermore, it has been found that the magnetic properties are enhanced when nanoparticles are used as fillers instead of microparticles. [ABSTRACT FROM AUTHOR]

In this work, a kinetic study is presented analyzing the influence of the initial pH on (PFasa) cellulase production by an Aspergillus niger strain, cultured in solid-state fermentation. The results showed that the optimum value of initial pH for PFasa production was 4.5. The PFasa activity reached 25.11 UI/gMS in 18 hours and a productivity of 1.40 UI h-1gMS-1 under these initial pH conditions. [ABSTRACT FROM AUTHOR]

The capability of Halobacterium sp. NRC-1 to synthesize carboxyl ester hydrolases was investigated, and the effect of physicochemical conditions on the growth rate and production of esterases was evaluated. The haloarchaeon synthesized a carboxyl ester hydrolase, confirming the genomic prediction. This enzymatic activity was intracellularly produced as a growth-associated metabolite. Esterase activity was assayed using different p-nitrophenyl-esters and triacyl-glycerides, which showed a preference for hydrolyzing tributyrin. The archaeal growth rate and esterase production were significantly influenced by the pH and the NaCl concentration. An interaction effect between temperature and NaCl was also seen. The maximal growth rate and esterase production found for Halobacterium sp. NRC-1 were 0.136 h−1 (at 4.2 M NaCl, pH 6 and 44°C) and 1.64 U/l (at 4.6 M NaCl, pH 6 and 30°C), respectively. Furthermore, the effects of NaCl concentration, pH and temperature on enzyme activity were studied. Two maximal esterase activities were elucidated from the intracellular crude extract when it was incubated at different NaCl concentrations (1 M and 5 M) and at different pHs (6 and 7.5). This is the first report that shows experimentally the synthesis of carboxyl ester hydrolases by Halobacterium sp. NRC-1. This enzyme was found to be extremely halophilic (5 M NaCl) and thermophilic (80°C), making it very interesting for future investigations in non-aqueous biocatalysis. [ABSTRACT FROM AUTHOR]

The present study was conducted to investigate the capability of Haloarcula marismortui to synthesize esterases and lipases, and the effect of physicochemical conditions on the growth and the production of esterases and lipases. Finally, the effect of NaCl concentration and temperature on esterase and lipase activities was studied using intracellular crude extracts. In order to confirm the genomic prediction about the esterase and lipase synthesis, H. marismortui was cultured on a rich medium and the crude extracts (intra- or extracellular) obtained were assayed for both activities using p-nitrophenyl esters and triacylglycerides as substrates. Studies on the kinetics of growth and production of esterase and lipase of H. marismortui were performed, reaching a maximum growth rate of 0.053 h−1 and maximal productions of intracellular esterase and lipase of 2.094 and 0.722 U l−1 using p-nitrophenyl valerate and p-nitrophenyl laurate, respectively. Both enzymes were produced as growth-associated metabolites. The effects of temperature, pH, and NaCl concentration on the growth rate and production of enzymes were studied by using a Box–Behnken response surface design. The three response variables were significantly influenced by the physicochemical factors and an interaction effect between temperature and NaCl concentration was also evidenced. The surface response method estimated the following maximal values for growth rate and productions of esterase and lipase: 0.086 h−1 (at 42.5°C, pH 7.4, and 3.6 mol l−1 NaCl), 2.3 U l−1 (at 50°C, pH 7.5, and 4.3 mol l−1 NaCl), and 0.58 U l−1 (at 50°C, pH 7.6, and 4.5 mol l−1 NaCl), respectively. Esterases were active at different salt concentrations, showing two optimal activities (at 0.5 and 5 mol l−1 NaCl), which suggested the presence of two different esterases. Interestingly, in the absence of salt, esterase retained 50% residual activity. Esterases and lipase activities were maximal at 45°C and inactive at 75°C. This study represents the first report evidencing the synthesis of esterase and lipase by H. marismortui. [ABSTRACT FROM AUTHOR]

• The fermented solid was used in the kinetic resolution of secondary alcohols. • The lipases in the fermented solid have anti-Kazlauskas enantiopreference. • The best results were a conversion of 23 % and an enantiomeric ratio (E SR) of 26. • The fermented solid has potential to reduce costs of kinetic resolutions. Lipases are widely used as biocatalysts in the resolution of racemates, where high chemo-, regio- and enantioselectivity are required. In this work, we produced lipases by culturing Rhizopus microsporus in solid-state fermentation. After the fermentation, the solids were dried, producing " Rhizopus microsporus fermented solids" (RMFS). The lipases in RMFS had high activity in the synthesis of ethyl oleate in n -heptane, retaining 100 % activity after 23 successive esterification cycles, each for 4 h at 40 °C. In the kinetic resolution of three aromatic secondary alcohols by transesterification with isopropenyl acetate, in n -heptane, RMFS showed preference for the (S)-enantiomers, in other words, an anti-Kazlauskas enantiopreference. The best results were a conversion of 23 % and an enantiomeric ratio (E SR , i.e. S relative to R) of 26 for resolution of (RS)-1-phenyl-1-ethanol, after 96 h at 40 °C. Since it is rare for lipases to have an (S)-enantiopreference, RMFS have the potential as low-cost biocatalysts for the resolution of racemates of secondary alcohols. [ABSTRACT FROM AUTHOR]