Studies on the α-amylase production were carried out with a bacterial strain isolated from a soil sample. The cells were cultivated in a mineral medium containing soluble starch as sole carbon source. The addition of calcium (10 mM) or peptone (1%) and yeast extract (0.5%) to the mineral medium shortened the lag period and improved the growth and α-amylase synthesis. The addition of glucose to the culture diminished greatly the synthesis of α-amylase, demonstrating that a classical glucose effect is operative in this organism. The optimum temperature and initial medium pH for amylase synthesis by the organism were 50°C and 7.0 respectively. The optimal pH and temperature for activity were 6.0 and 50°C respectively. The enzyme extract retained 100% activity when incubated for one hour at 90°C and 40% at 60°C for 24 h. The addition of glucose to the culture diminished greatly the synthesis of α-amylase.

Lipid transfer proteins (LTP) facilitate transfer of lipids between membranes in vitro. Up to now, they have been found to be localized basically in the plant cell wall and in compartments linked to lipid metabolism, such as glyoxysomes. Accordingly, LTP are considered to be involved in the plant defence against pathogen microbes and lipid metabolism. We herein show, by immunoelectron microscopy, that besides the cell wall, LTP are localized in the lumen of organelles which we suggest to be the protein storage vacuoles, as well as in vesicles similar to the lipid‐containing ones and in the extracellular space of Vigna unguiculata seeds. To further characterize these organelles, we performed subcellular fractionation of membranes isolated from imbibed seeds on a sucrose‐density gradient. The analysis of these fractions revealed that the lightest membrane vesicles, derived probably from PSV, contain LTP, α‐TIP and K+ independent PPiase, but not γ‐TIP and K+ stimulated PPiase. The presence of LTP and vicilins (typical storage protein) in the lumen of these vesicles was confirmed by immunoelectron microscopy. Taken together, the data suggest that the intracellular LTP in the V. unguiculata seeds are localized in protein storage vacuoles and in lipid‐containing vesicles.

In this work, we theoretically analyze how a passive solute is transported by an oscillating electro-osmotic flow along a parallel flat plate microchannel connecting two reservoirs with different concentrations. Three distinct periodic functions of the applied external electric field are considered: sawtooth, square, and parabolic waveforms, which are expressed as Fourier series. For each case, the dimensionless velocity and concentration fields are found analytically and, subsequently, the transport of the solute was obtained numerically. We distinguish four dimensionless parameters that govern the studied phenomenon: an angular Reynolds number, the Schmidt and Péclet numbers, and an electrokinetic parameter, this latter representing the ratio of the half-height of the microchannel to the Debye length. As has been reported in the specialized literature, the mass transport and separation of species in oscillating flows under the effect of an oscillatory pressure gradient can be increased with the angular frequency. For the present study, instead of a pressure gradient, we use oscillatory electro-osmotic forces, together with symmetric and asymmetric wall zeta potentials in the microchannel. For this condition, we prove that the transport of the solute is affected notably. In this paper, we show that controlling the type of the external electrical signal can also improve the mentioned tasks, depending on the Schmidt number, the electrokinetic parameter, and the angular Reynolds number.

The search for alternatives for the control of microbiological contamination in foods has been the object of study in different scientific areas. This study aimed to evaluate the efficiency of lemon grass (Cymbopogon citratus) essential oil in controlling the growth of the fungus Aspergillus flavus in three types of analysis: first, by in vitro tests, in essential oil doses between 0.2 and 1.0 μL/ml; second, by serial microdilution to determine the minimum inhibitory concentration, in doses between 0.1 and 1.2 μL/mL; and third, by inhibition of fungal growth in corn kernels contaminated using essential oil doses of 0.4, 0.7, and 1.0 μL/mL, in the incubation times of 14, 28, and 42 days. The in vitro tests showed that the essential oil controlled the fungus from doses of 0.6 μL/mL, but the dose of 1.0 μL/mL controlled 100% growth until day eight of incubation, from which it decreased. The minimum inhibitory concentration for the microdilution analysis was 0.9 μL/mL. The evaluation of the corn kernels for all doses of essential oil and times tested showed 100% inhibition of the fungal growth.

Fungi are among the main responsible for damage and loss in various foods. They have the ability to produce secondary metabolites when subjected to ideal conditions, known as mycotoxins, highly toxic substances that can contaminate products intended for both human and animal food causing damage to health. The control of these fungi has been done through synthetic substances, which are harmful to man and the environment. Thus, it is necessary to search for alternative methods of controlling these microorganisms. In this context, essential oils are a possible option. The objective of this study was to identify the main components and evaluate the effectiveness of the essential oil of rosemary (Rosmarinus officinalis) for controlling the fungus Aspergillus flavus. Initially, the effect of essential oils on mycelial growth of the fungus was verified in in vitro tests at doses of: 0.8; 1.6; 3.2; 6.4; 12.8; 15; 17.5; 20; 22.5 and 25 µL/mL, this being the dose with the greatest fungal control. Based on the results of the in vitro tests, serial microdilution was performed in microplates to find the minimum inhibitory concentration, which was 25 µL/mL. The results showed that the essential oil showed fungicidal potential on A. flavus. The main components of the essential oil, identified by gas chromatography, in order of concentration, were: 1,8-cineol, camphor and β-pinene.