Estudo da humidade e actividade de água de pranchas de cortiça durante o processo de fabrico de rolhas de cortiça - resultados preliminares

The main goal of this work was to make evidence of the applicability in the cork stopper industry of a control method along the cork slabs maturing stage after boiling, aiming to ensure the adequate conditions for Chrysonilia sitophila colonisation of cork slabs during that period, avoiding the development of other fungi. Cork humidity and water activity (wa) were used as indicators. Comparing the drying rate of the outer and the inner parts of the bark it could be observed, under the assay conditions, that to attain 0.9 wa, (the critical point for C. sitophila development), 39.8h were necessary in the case of outer bark while inner bark only need 20.4h. As the visible part of the cork slabs corresponds more to its outer part, the time of 40h can be taken as a good visible indicator to limit the cork slabs maturing period after boiling. Moreover it could be observed that under that period of time the evident prevailing fungus on the cork slabs was C. sitophila so probably assuring low probabilities of ‘cork taint’ occurrence, under the conditions propose on this study

In Vitro Reassembly of the Malolactic Fermentation Pathway of Leuconostoc oenos (Oenococcus oeni)

The mechanism of metabolic energy generation by malolactic fermentation was studied with artificial membrane vesicles of Leuconostoc oenos (Oenococcus oeni). (Note that although L. oenos was recently reclassified as O. oeni, the old designation was kept in the present work.) Purified malolactic enzyme was entrapped in artificial membrane vesicles prepared from L. oenos cells able to transport L-malate. We show that the in vitro reconstituted system, including an electrogenic L-malate carrier and the decarboxylating malolactic enzyme, generated a proton motive force that was able to drive intravesicular accumulation of leucine.

The proton motive force generated in Leuconostoc oenos by L-malate fermentation

In cells of Leuconostoc oenos, the fermentation of L-malic acid generates both a transmembrane pH gradient, inside alkaline, and an electrical potential gradient, inside negative. In resting cells, the proton motive force ranged from -170 mV to -88 mV between pH 3.1 and 5.6 in the presence of L-malate. Membrane potentials were calculated by using a model for probe binding that accounted for the different binding constants at the different pH values at the two faces of the membrane. The Delta psi generated by the transport of monovalent malate, H-malate(-), controlled the rate of fermentation. The fermentation rate significantly increased under conditions of decreased Delta psi, i.e., upon addition of the ionophore valinomycin in the presence of KCl, whereas in a buffer depleted of potassium, the addition of valinomycin resulted in a hyperpolarization of the cell membrane and a reduction of the rate of fermentation. At the steady state, the chemical gradient for H-malate(-) was of the same magnitude as Delta psi. Synthesis of ATP was observed in cells performing malolactic fermentation.</p

The Proton Motive Force Generated in Leuconostoc oenos by L-Malate Fermentation

In cells of Leuconostoc oenos, the fermentation of L-malic acid generates both a transmembrane pH gradient, inside alkaline, and an electrical potential gradient, inside negative. In resting cells, the proton motive force ranged from -170 mV to -88 mV between pH 3.1 and 5.6 in the presence of L-malate. Membrane potentials were calculated by using a model for probe binding that accounted for the different binding constants at the different pH values at the two faces of the membrane. The Δψ generated by the transport of monovalent malate, H-malate-, controlled the rate of fermentation. The fermentation rate significantly increased under conditions of decreased Δψ, i.e., upon addition of the ionophore valinomycin in the presence of KCl, whereas in a buffer depleted of potassium, the addition of valinomycin resulted in a hyperpolarization of the cell membrane and a reduction of the rate of fermentation. At the steady state, the chemical gradient for H-malate- was of the same magnitude as Δψ. Synthesis of ATP was observed in cells performing malolactic fermentation.

New insights concerning the occurrence of fungi in water sources and their potential pathogenicity

Fungi are known to occur ubiquitously in the environment. In the past years, the occurrence of filamentous fungi in the aquatic environment has been a subject of growing interest. This study describes the occurrence of various fungal genera in different drinking water sources being Penicillium and Trichoderma the most representative ones (30% and 17%, respectively). Also, 24 fungal species that have not been previously described in the aquatic environment are reported in this study, being once again the major species from the Penicillium genera. This study therefore contributes to the knowledge on the richness of fungi diversity in water. 68% of the described species were found to be able to grow at 30°C but only Aspergillus fumigatus, Aspergillus viridinutans and Cunninghamella bertholletiae were able to grow at the higher temperature tested (42°C). 66% of the species that were able to grow at 30°C have spore sizes below 5μm which enables them to cause breathing infections. These were therefore identified as potential pathogenic species. © 2013 Elsevier Ltd