R.O.M.A. de Souza

Heteroduplex mobility assay of the D1/D2 region of the 26S rDNA for differentiation of Saccharomyces species.

Aims: We present the HMA method for Saccharomyces differentiation using the PCR amplified D1/D2 26S rDNA.

Microwave-assisted extraction of green coffee oil and quantification of diterpenes by HPLC

The microwave-assisted extraction (MAE) of 13 different green coffee beans (Coffea arabica L.) was compared to Soxhlet extraction for oil obtention. The full factorial design applied to the microwave-assisted extraction (MAE), related to time and temperature parameters, allowed to develop a powerful fast and smooth methodology (10 min at 45°C) compared to a 4h Soxhlet extraction. The quantification of cafestol and kahweol diterpenes present in the coffee oil was monitored by HPLC/UV and showed satisfactory linearity (R(2)=0.9979), precision (CV 3.7%), recovery (<93%), limit of detection (0.0130 mg/mL), and limit of quantification (0.0406 mg/mL). The space-time yield calculated on the diterpenes content for sample AT1 (Arabica green coffee) showed a six times higher value compared to the traditional Soxhlet method.

Microwave-assisted methanolysis of green coffee oil

Optimisation of a microwave-assisted methanolysis was performed to obtain cafestol and kahweol directly from green coffee oil (Coffea arabica). A two-factor (the methanolysis period and temperature), three-level, factorial experimental design (3(2)) was adopted. The methanolysis procedure was performed under microwave irradiation, using closed vessel and accurate fast responding internal fibre-optic temperature probe. The effects on the responses were measured by HPLC. After 3 min of microwave irradiation (hold time) at 100°C, with 500 mg of green coffee oil, a yield higher than 99% was obtained. The yield of this reaction is 26% after 2h when working under conventional heating. The methods described in the literature lead to long reaction times, poor yields and formation of side products. The microwave-assisted technique proved to be faster, avoided undesired side products and gave better conversion, when compared to conventional heating process.

Theoretical Aspects of Microwave Irradiation Practices

In the field of organic chemistry, microwave irradiation proved to be a powerful method to enhance chemical processes. In many instances, the use of sealed-vessel high-temperature microwave processing was able to dramatically reduce reaction times, consume less solvent, increase yields, reduce side reactions and improve reproducibility. Microwaves are known to be a more efficient heating method than traditional thermal process where reactions that require long reflux times can sometimes be carried out in a few hours or minutes in a dedicated microwave irradiation equipment.

A comparison of concentration measurement techniques for the estimation of the apparent mass diffusion coefficient

In this article we compare two different techniques to measure the concentration of saline solutions for the identification of the apparent mass diffusion coefficient in soils saturated with distilled water. They are the radiation measurement technique and the electrical conductivity measurement technique. These techniques are compared in terms of measured quantities, sensitivity coefficients with respect to unknown parameters and the determinant of the information matrix. The apparent mass diffusion coefficient is estimated by utilizing simulated measurements containing random errors. The Levenberg-Marquardt method of minimization of the least-squares norm is used as the parameter estimation procedure. The effects of the volume of saline solution injected into the column devised for the experiments on the accuracy of the estimated parameters are also addressed in this article.

Enantioselective biotransformation of sterically hindered amine substrates by the fungus Stemphylium lycopersici

To screen 20 micro‐organisms for ω‐transaminase (ω‐TA) activity by the kinetic resolution of rac‐1‐phenylethylamine, followed by testing rac‐amines of pharmaceutical interest with bulky substituents and to conduct the asymmetric synthesis of a chiral amine.

A general particle stress equation for fixed and fluidised beds

Abstract A general constitutive equation is proposed for the solid particle stress in a fluidised bed. This equation reduces in a straightforward manner to describe the particle stress in a fixed bed, and it implies a Mohr-Coulomb yield criterion for the transition from the fixed-bed to the fluidised-bed state. Experimental evidence is given to show that at incipient fluidisation, the particle stress assumes a form agreeing with that predicted by theory.