http://hdl.handle.net/10362/3585 2013-05-19T10:16:46Z http://hdl.handle.net/10362/8554 Title: Biogenic amines in wine: gene transcription as a tool for selection of Oenococcus oeni starter strains Authors: Marques, Ana Paula Gomes Abstract: Wine is a complex environment where the microbial flora can have both a positive (e.g. malolactic fermentation) and a negative (e.g. production of biogenic amines) impact on the quality of wine. Biogenic amines are nitrogenous compounds of low molecular weight that can be found in fermented food and beverages, including wine. Biogenic amines are formed primarily by decarboxylation of the corresponding amino acids by microorganisms through substrate-specific decarboxylases. Some authors consider the presence of biogenic amines to be a fundamental parameter for detriment of alcoholic beverages. These compounds can have adverse health effects on sensitive individuals at high concentrations. The role of microorganisms in wine involves two important fermentation processes, the alcoholic fermentation conducted by yeasts and the malolactic fermentation conducted by lactic acid bacteria. The malolactic fermentation refers to the conversion of L-malic acid into L-lactic acid and CO2, catalysed by the malolactic enzyme. This mechanism contributes for deacidification, bacterial stability and flavour changes in wine. Oenococcus oeni is the leading lactic acid bacteria responsible for malolactic fermentation, mainly due to its adaptability to such a chemically harsh wine environmental (low pH and high ethanol concentrations). The two main goals of this PhD thesis were to contribute to the: (1) increase of knowledge of biogenic amines occurrence in wine; (2) oenological characterization and selection of Portuguese autochthonous O. oeni strains, isolated from different winemaking regions, to be used as malolactic starters on the wine industry.(...) Description: Dissertation presented to obtain the Ph.D degree in Biology 2012-01-01T00:00:00Z http://hdl.handle.net/10362/6860 Title: Dynamics of cork mycobiota throughout stopper manufacturing process: from diversity to metabolite Authors: Barreto, Maria do Carmo Abstract: Cork, the continuous layer of outer bark of the Quercus suber L. tree, has physical and chemical properties that are unique. Portugal possesses 33 % of the world’s cork oak forests and accounts for approximately half of total global cork production. The manufacture of cork discs (or stoppers) comprises several stages, including two boiling stages, during which slabs of cork are steeped in boiling water. In days following the boiling the humidity of the slabs decreases and they become completely covered in a white mycelium of Chrysonilia sitophila until the cork achieves a certain water activity level (ca 0.9 aw). Below this level other fungal species (e.g. Penicillium, Aspergillus or Trichoderma) can germinate and shift the fungal colonization of the cork slabs. The two main objectives of the research described in the presented PhD thesis are (1) a taxonomic identification of the mycobiota present in cork slabs throughout the manufacture of cork discs, and (2) an investigation into the chemical compounds, which can give unfavourable properties to the cork, produced by these fungi.(...) Description: Dissertation presented to obtain the Ph.D degree in Biology 2011-12-01T00:00:00Z http://hdl.handle.net/10362/3755 Title: Penicillium glabrum cork colonising isolates – preliminary analysis of their genomic similari Authors: Basílio, MC; Gaspar, R; Silva, Pereira C; San, Romão MV Abstract: Cork stopper manufacturing process includes an operation, known as stabilisation, by which humid cork slabs are extensively colonised by fungi. The effects of fungal growth on cork are yet to be completely understood and are considered to be involved in the so called “cork taint” of bottled wine. It is essential to identify environmental constraints which define the appearance of the colonising fungal species and to trace their origin to the forest and/or as residents in the manufacturing space. The present article correlates two sets of data, from consecutive years and the same season, of systematic biologic sampling of two manufacturing units, located in the North and South of Portugal. Chrysonilia sitophila dominance was identified, followed by a high diversity of Penicillium species. Penicillium glabrum, found in all samples, was the most frequent isolated species. P. glabrum intra-species variability was investigated using DNA fingerprinting techniques revealing highly discriminative polymorphic markers in the genome. Cluster analysis of P. glabrum data was discussed in relation to the geographical location of strains, and results suggest that P. glabrum arise from predominantly the manufacturing space, although cork resident fungi can also contrib 2006-01-01T00:00:00Z http://hdl.handle.net/10362/3754 Title: Screening pentachlorophenol degradation ability by environmental fungal strains belonging to the phyla Ascomycota and Zygomycota Authors: Carvalho, M. B.; Martins, I.; Leitão, M. C.; Garcia, H.; Rodrigues, C.; San Romão, M. Vitória; McLellan, I.; Hursthouse, A.; Pereira, Cristina Silva Abstract: Pentachlorophenol (PCP) bioremediation by the fungal strains amongst the cork- colonising community has not yet been analysed. In this paper, the co- and direct metabolism of PCP by each of the 17 fungal species selected from this community were studied. Using hierarchical data analysis, the isolates were ranked by their PCP bioremediation potential. Fifteen isolates were able to degrade PCP under co-metabolic conditions, and surprisingly Chrysonilia sitophila, Trichoderma longibrachiatum, Mucor plumbeus, Penicillium janczewskii and P. glandicola were able to directly metabolise PCP, leading to its complete depletion from media. PCP degradation intermediates are preliminarily discussed. Data emphasise the signiWcance of these fungi to have an interesting potential to be used in PCP bioremediation processes. 2010-01-01T00:00:00Z