Abstract This paper evaluated the drying kinetics at different temperatures and the effect of the drying temperature on the physical-chemical properties and active compounds of the residue from the industrial processing of camu-camu. The drying temperatures of 40, 50, and 60 °C were evaluated. The residues dried at different temperatures were characterized in terms of their pH, water activity, anthocyanins, flavonoids, carotenoids, phenolic compounds and Fourier transform infrared spectroscopy. The parameters of the Page model showed the best adjustments to the experimental data. Drying affected the concentration of active compounds in the camu-camu residue. At 60 °C, the degradation of flavonoids, anthocyanins, and phenolic compounds was lower than in the dry residue, possibly because less time was required to achieve equilibrium in moisture content. Thus, in order to maintain higher concentrations of active compounds in the residue, drying at higher temperatures is recommended.

Atomic Force Microscopy (AFM) can be used to obtain high-resolution topographical images of bacteria revealing surface details and cell integrity. During scanning however, the interactions between the AFM probe and the membrane results in distortion of the images. Such distortions or artifacts are the result of geometrical effects related to bacterial cell height, specimen curvature and the AFM probe geometry. The most common artifact in imaging is surface broadening, what can lead to errors in bacterial sizing. Several methods of correction have been proposed to compensate for these artifacts and in this study we describe a simple geometric model for the interaction between the tip (a pyramidal shaped AFM probe) and the bacterium (Escherichia coli JM-109 strain) to minimize the enlarging effect. Approaches to bacteria immobilization and examples of AFM images analysis are also described.

Analizou-se o papel do exopolissacarídeo (EPS) no mecanismo de resistência ao Cu2+ da Xanthomonas axonopodis pv. citri (Xac) com as espectroscopias de infravermelho com transformada de Fourier (FTIR), ressonância paramagnética eletrônica (RPE) e ressonância magnética nuclear (RMN). Os dados de FTIR demonstraram que as células cultivadas na presença de 0.2 mmol L-1 de CuSO4 produziram uma maior quantidade de exopolissacarídeo piruvatado do que as células cultivadas na sua ausência. Os dados de RPE indicaram que a quantidade de íons Cu2+ diminuiu com o tempo de cultura. Os dados de RMN de 13C mostraram a complexação dos íons de Cu2+ com o EPS. Esses resultados mostraram que o EPS tem um papel importante no mecanismo de proteção da Xac ao Cu2+ e este age no mecanismo inicial de proteção, ligando-se aos íons de Cu2+ livres, reduzindo sua difusão e o transporte ativo ao citoplasma . O Cu2+ também induz a produção de EPS piruvatado, que aumenta a capacidade de coleta e complexação desses íons.

We analyzed the role of exopolysaccharide in the Xanthomonas axonopodis pv. citri (Xac) Cu2+ resistance mechanism by Fourier transform infrared (FTIR), electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopies. The FTIR data show that cells cultivated in the presence of 0.2 mmol L-1 of CuSO4 produce larger amounts of pyruvated exopolissacharide (EPS) than the ones cultivated in its absence. The EPR data indicate that the amount of Cu2+ decreases with cultivation time. The 13C-CPMAS NMR data also show the complexation of Cu2+ ions to the EPS. The results demonstrate that EPS plays an important role in Xac Cu2+ protection. Both capsular and slime EPS act as an initial protection mechanism, binding free Cu2+ ions, reducing their diffusion and their active transport to the cytoplasm. Cu2+ also induces the production of a highly pyruvated negative EPS, increasing its capture and binding capacity.