Production of Aspergillus niger GH1 tannase using solid-state fermentation

The production of tannase by Aspergillus niger GH1 in solid-state fermentation (SSF) was evaluated. Several concentrations of tannic acid (12.5, 25, 50 and 100 g/L) were tested in a model culture system. Column reactors were packed with polyurethane foam impregnated with liquid medium and inoculated with fungal spores. Tannase production was kinetically monitored by 48 h. Tannic acid uptake was spectrophotometrically measured and extracellular and intracellular tannase activities were assayed by HPLC-chromatography. Tannase activity increased with increasing concentration of tannic acid. Maximum extracellular and intracellular tannase activities (11.35 and 6.95 U/mL respectively) were recorded with 100 g/L of tannic acid. The substrate uptake was 100% at concentrations of 12.5, 25 and 50 g/L, while 74.4% was consumed in the presence of 100 g/L of tannic acid after 48 h of culture. These results suggest that high concentrations of tannins can be removed by SSF and tannase production can be reached in high levels.The present work was performed as part of a cooperative agreement between the Universidad Autonoma de Coahuila (UAdeC, Mexico) and the Universidade do Minho (UM, Portugal) within a specific international exchange program (VALNATURA project, alfa network from European Union) undertaken at the Biological Engineering Department (UM, Portugal) M A Cruz-Hernandez thanks to Concejo nacional de Ciencia y Tecnologia (CONACYT) the fellowship to study the doctoral program at the Department of Biotechnology (UAdeC

Electrochemical Impedance Spectroscopy (EIS): A Review Study of Basic Aspects of the Corrosion Mechanism Applied to Steels

AC impedance measurements have been applied for over twenty years in electrochemistry and physics to investigate the electrical properties of conductive materials and their interfaces using an external electrical impulse (VOLTAGE, V or CURRENT, I) as driving force. Furthermore, its application has recently appeared to be destined in the Biotechnology field as an effective tool for rapid microbiologic diagnosis of living organism in situ. However, there is no doubt that the electrochemical impedance spectroscopy (EIS) is still one of the most useful techniques around the world for metal corrosion control and its monitoring. Corrosion has long been recognized as one of the most expensive stumbling blocks that concern many industries and government agencies, because it is a steel destructive phenomenon that occurs due to the chemical interaction with aqueous environments and takes place at the interface between metal and electrolyte producing an electrical charge transfer or ion diffusion process. Consequently, it is experimentally possible to determine through the EIS technique the mechanism and control that kinectics of corrosion reactions encounter. First, EIS data is collected through a potentiostat/ galvanostat apparatus. After, it is fitted to a mathematical model (i.e. an equivalent electrical circuit, EEC) for its interpretation and analysis, fundamentally seeking a meaningful physical interpretation. Finally, this review reports some basic aspects of the corrosion mechanism applied to steels through the experimental EIS response using Nyquist or Bode plots. Examples are given for different applied electrochemical impedance cases in which steel is under study intentionally exposed to a corrosive aqueous solution by applying a sinusoidal potential at various test conditions

Preliminary culture conditions for Aspergillus niger GH1 tannase production in submerged culture

Nowadays, tannase is produce by submerged culture (SmC) being the enzyme obtained in an intracellular form resulting, as a consequence, in high production costs. To demonstrate that fungal tannase excretion is strongly influenced by the culture conditions, tannase production by Aspergillus niger GH1 on SmC using different bioreactors was evaluated. Two sets of experiments were conducted using in a first step a 1.5 L bioreactor and in a second step 100 mL erlenmeyer flasks. Modifications to culture conditions previously reported allowed to obtain positive results for tannase production in SmC, being the selected conditions: initial pH 5, temperature 35°C, initial substrate concentration 25g/L and agitation 200 rpm.A cultura submersa (SmC) é o processo empregado para produzir comercialmente a enzima tanasa, porém neste sistema da cultura, a tanasa é expressada principalmente de maneira intracelular o que representa custos de produção elevados. Para demonstrar que a excreção da tanasa do fungo está fortemente influenciada pelas condições da cultura, a produção da enzima tanase por Aspergillus niger GH1 em SmC foi avaliada. Dois conjuntos de experiências foram conduzidos usando em uma etapa um fermentador de 1.5 L e em uma segunda etapa matrazes (erlenmeyers) de 100 mL. As modificações às condições da cultura previamente descritas permitiram a obtenção de resultados positivos para a produção do tannase neste modo de produção, tendo sido definidas as seguintes condições de cultura: pH inicial 5, concentração inicial de substrato 25g/L, temperatura 35°C e agitação 200 rpm

A Mathematical Model to Optimize the Neoadjuvant Chemotherapy Treatment Sequence for Triple-Negative Locally Advanced Breast Cancer

Background: Triple-negative locally advanced breast cancer is an aggressive tumor type. Currently, the standard sequence treatment is applied, administering anthracyclines first and then a taxane plus platinum. Clinical studies for all possible treatment combinations are not practical or affordable, but mathematical modeling of the active mitotic cell population is possible. Our study aims to show the regions with the tumor’s most substantial cellular population variation by utilizing all possible values of the parameters () that define the annihilatory drug capacity according to the proposed treatment. Method: A piecewise linear mathematical model was used to analyze the cell population growth by applying four treatments: standard sequences of 21 days (SS21) and 14 days (SS14), administering anthracyclines first, followed by a taxane plus platinum, and inverted sequences of 21 days (IS21) and 14 days (IS14), administering a taxane plus platinum first then anthracyclines. Results: The simulation showed a higher effect of IS14 over SS14 when the rate of drug resistance was larger in the cell population during DNA synthesis (G1 and S) compared to cells in mitosis (G2 and M). However, if the proportion of resistant cells in both populations was equivalent, then treatments did not differ. Conclusions: When resistance is considerable, IS14 is more efficient than SS14, reducing the tumor population to a minimum

Looking the void in the eyes - the kSZ effect in LTB models

As an alternative explanation of the dimming of distant supernovae it has recently been advocated that we live in a special place in the Universe near the centre of a large void described by a Lemaitre-Tolman-Bondi (LTB) metric. The Universe is no longer homogeneous and isotropic and the apparent late time acceleration is actually a consequence of spatial gradients in the metric. If we did not live close to the centre of the void, we would have observed a Cosmic Microwave Background (CMB) dipole much larger than that allowed by observations. Hence, until now it has been argued, for the model to be consistent with observations, that by coincidence we happen to live very close to the centre of the void or we are moving towards it. However, even if we are at the centre of the void, we can observe distant galaxy clusters, which are off-centre. In their frame of reference there should be a large CMB dipole, which manifests itself observationally for us as a kinematic Sunyaev-Zeldovich (kSZ) effect. kSZ observations give far stronger constraints on the LTB model compared to other observational probes such as Type Ia Supernovae, the CMB, and baryon acoustic oscillations. We show that current observations of only 9 clusters with large error bars already rule out LTB models with void sizes greater than approximately 1.5 Gpc and a significant underdensity, and that near future kSZ surveys like the Atacama Cosmology Telescope, South Pole Telescope, APEX telescope, or the Planck satellite will be able to strongly rule out or confirm LTB models with giga parsec sized voids. On the other hand, if the LTB model is confirmed by observations, a kSZ survey gives a unique possibility of directly reconstructing the expansion rate and underdensity profile of the void.Comment: 20 pages, 9 figures, submitted to JCA

Visualization of the flow distribution inside the piston displacement of a gamma-type stirling engine

The dynamics of the confined flow inside the piston displacement of a Gamma-type Stirling engine operating as a heat pump is experimentally analyzed. The diameter of the piston is 30 mm; 2 mm smaller than the internal diameter of the cold cylinder. As the piston performs its reciprocating motion, the gas leaks around the gap between the piston and the cylinder wall, generating a continuous pulsating motion. In the first part of the cycle air is introduced and compressed by the piston motion, and then the second part of the cycle starts by expanding the air and ejecting it from the assembly chamber. Experimental observations were carried out at frequencies in the range 100 to 300 rpm. The flow was visualized using a vertical laser beam plane oriented in the same axial direction of the piston’s motion. The particles used as trackers are water drops condensed on carbon dioxide microcrystals. Images were taken with a high speed video camera with a frame rate of 1000 fps. PIV techniques were implemented to identify the flow main structures. For analysis purposes, fixed phase averages of the velocity fields are required, due to the turbulent regime observed in this phenomena and its oscillatory nature. Based on experimental measurements it can be demonstrated that the average flow involved is not axisymmetric, although very interestingly, specific inlet and exit regions of the piston-cylinder gap were identified.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016