Browsing by Author "Caldeira, Jorge"
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- Dominance of Saccharomyces cerevisiae in wine fermentations: secretion of antimicrobial peptides and microbial interactionsPublication . Albergaria, Helena; Branco, Patricia; Francisco, Diana; Coutinho, Rute; Monteiro, Margarida; Malfeito-Ferreira, Manuel; Arneborg, Nils; Almeida, M. Gabriela; Caldeira, JorgeIn present work we investigated the antagonistic effect by S. cerevisiae against several wine-related microbial species vis-à-vis the secretion of antimicrobial peptides (AMPs).
- Effect of saccharomycin, a natural Saccharomyces cerevisiae biocide, on Hanseniaspora guilliermondii cells surfacePublication . Calvário, Joana; Silva, Nelly; Almeida, M. Gabriela; Albergaria, Helena; Eaton, Peter; Macedo, Anjos L.; Caldeira, JorgeABSTRACT: During spontaneous wine fermentations, most of the non-Saccharomyces yeasts present in grape musts show an early decline in their population. It was traditionally assumed that Saccharomyces cerevisiae (S.c.) prevalence was due to the higher resistance of this species to ethanol. However, wine fermentations performed with single cultures of non-Saccharomyces strains showed that those strains could withstand much higher ethanol levels [1]. It was then found that S.c. (strain CCMI 885) produced antimicrobial peptides (AMPs) that are responsible for the early death of the non Saccharomyces yeasts [2]. In previous work, we isolated, purified and sequenced those ntimicrobial peptides (AMPs) and found that they derive from the glyceraldehyde 3-phosphate dehydrogenase enzyme [3]. These GAPDH-derived AMPs compose the natural biocide secreted by S.c., which we named saccharomycin, and are effective against sensitive yeasts both in its natural/isolated and synthetic form.
- Identification of novel GAPDH-derived antimicrobial peptides secreted by Saccharomyces cerevisiae and involved in wine microbial interactionsPublication . Branco, Patricia; Francisco, Diana; Chambon, Christophe; Hébraud, Michel; Arneborg, Nils; Gabriela Almeida, M.; Caldeira, Jorge; Albergaria, HelenaSaccharomyces cerevisiae plays a primordial role in alcoholic fermentation and has a vastworldwide application in the production of fuel-ethanol, food and beverages. The dominance of S. cerevisiae over other microbial species during alcoholic fermentations has been traditionally ascribed to its higher ethanol tolerance. However, recent studies suggested that other phenomena, such as microbial interactions mediated by killer-like toxins, might play an important role. Here we show that S. cerevisiae secretes antimicrobial peptides (AMPs) during alcoholic fermentation that are active against a wide variety of wine-related yeasts (e.g. Dekkera bruxellensis) and bacteria (e.g. Oenococcus oeni). Mass spectrometry analyses revealed that these AMPs correspond to fragments of the S. cerevisiae glyceraldehyde 3-phosphate dehydrogenase (GAPDH) protein. The involvement of GAPDH-derived peptides in wine microbial interactions was further sustained by results obtained in mixed cultures performed with S. cerevisiae single mutants deleted in each of the GAPDH codifying genes (TDH1-3) and also with a S. cerevisiae mutant deleted in the YCA1 gene, which codifies the apoptosis-involved enzyme metacaspase. These findings are discussed in the context of wine microbial interactions, biopreservation potential and the role of GAPDH in the defence system of S. cerevisiae.
- Oxidative stress and histological changes following exposure to diamond nanoparticles in the freshwater Asian clam Corbicula fluminea (Müller, 1774)Publication . Cid, António; Picado, Ana; Correia, J.B.; Chaves, Rúben; Silva, Héber; Caldeira, Jorge; Matos, A. Alves de; Diniz, M. S.Recently, the scientific community became aware of the potential ability of nanoparticles to cause toxicity in living organisms. Therefore, many of the implications for aquatic ecosystems and its effects on living organisms are still to be evaluated and fully understood. In this study, the toxicity of nanodiamonds (NDs) was assessed in the freshwater bivalve (Corbicula fluminea) following exposure to different nominal concentrations of NDs (0.01, 0.1, 1, and 10 mg l-1) throughout 14 days. The NDs were characterized (gravimetry, pH, zeta potential, electron microscopy, and atomic force microscopy) confirming manufacturer information and showing NDs with a size of 4–6 nm. Oxidative stress enzymes activities (glutathione-S-transferase, catalase) and lipid peroxidation were determined. The results show a trend to increase in GST activities after seven days of exposure in bivalves exposed to NDs concentrations (>0.1 mg l-1), while for catalase a significant increase was found in bivalves exposed from 0.01 to 1.0 mg l-1 following an exposure of 14 days. The histological analysis revealed alterations in digestive gland cells, such as vacuolization and thickening. The lipid peroxidation showed a trend to increase for the different tested NDs concentrations which is compatible with the observed cellular damage.
- Saccharomycin, a biocide from S. cerevisiae that kill-off other yeastsPublication . Caldeira, Jorge; Gabriela Almeida, M.; Macedo, Anjos L.; Silva, José P. M.; Albergaria, HelenaABSTRACT: Introduction: Saccharomyces cerevisiae plays an important role in alcoholic fermentation and is involved in the production of wine, beer and bread. Recent studies [1–7] showed that S. cerevisiae secretes antimicrobial peptides (AMPs), named “saccharomycin”, derived from the glycolytic enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH) that are active against a variety of wine-related microbial species. AMPs are low molecular weight proteins with broad antimicrobial spectrum of action against bacteria, viruses, and fungi [8]. Organisms use AMPs for defence against infection and membrane interaction appears to be the key to this antimicrobial function: generally they adopt amphiphilic structures that interact with the infectious agent’s membrane. AMPs constitute a promising source as alternatives to: i) combat pathogenic bacteria resistant to common antibiotics and ii) substitute chemical preservatives in food-fermented products such as wine. The aim of this study was to discover the mode of action of these peptides by detailed chemical structure characterisation and cell contact mechanism.
- Upgrade of PVAc-based glues for their application in wet environments and in structures:an industry-involving projectPublication . Santos, Joana; Fernandes, S.; Duarte, Carlota; Caldeira, Jorge; Santos, José António dosPolyvinyl acetate (PVAc)-based glues are very common in the furniture and joinery industries, among others, quite probably because they are relatively cheap and very easy to handle and apply. However, as the mechanism of gluing lies on the absorption of water by wood or wood derivatives, having as a consequence the coalescence of the polymer, their application is restricted to wood with less than 12% moisture content. Regarding the topic of the research work presented in short here, common PVAC glues have also fluency, meaning this that, once hardened, they are not stiff enough to be applied in glulam, for example, intended for structures, nor are they suitable for permanent or semi-permanent moist environments. This latter is because PVAc glues are reversible; i.e., moisture brings them to more or less their original liquid state. The aim of this research work was to upgrade common PVAc glues offered in the market, hence expanding their range of applications and enlarging their market opportunities, by the application of new crosslinkers of polyurethane nature specifically synthesised for purposes of this kind. The assessment of the quality of the gluelines to wood was carried out according to the appropriated testing European standards. The European standard EN 204:2001 - Classification of thermoplastic wood adhesives for non-structural applications, establishes classes from D1 less resistance to high moisture content to D4 maximum resistance to moisture content. normal PVAc glues usually classifies D2 which indicates preferential uses in occasional water contact and moisture content always below 18 % (interior), meanwhile D3 or D4 allow more frequent contact with water and occasional higher moisture contents, as it happens in exterior covered uses. Modified PVAc glues with addition of crosslinkers allowed this type of glues to improve from D2 to D3, opening the possibility of competing with solvent emission glues. The research team, that involved a chemical company, a wood products company, a group of researchers on polymer chemistry and a group of researchers on wood products, was successful in obtaining a glue formulation of D3 quality. The results from industrial-scale trials will also be reported. Actually, the synergy among companies and R&D organisations will also be highlighted.