Browsing by Author "Vasconcelos, Isabel"
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- 1,3-Propanediol production in a two-step process fermentation from renewable feedstockPublication . Mendes, Filipa Soares; González-Pajuelo, Maria; Cordier, Hélène; François, Jean M.; Vasconcelos, IsabelIn this work, the production of 1,3-propanediol from glucose and molasses was studied in a two-step process using two recombinant microorganisms. The first step of the process is the conversion of glucose or other sugar into glycerol by the metabolic engineered Saccharomyces cerevisiae strain HC42 adapted to high (>200 g l−1) glucose concentrations. The second step, carried out in the same bioreactor, was performed by the engineered strain Clostridium acetobutylicum DG1 (pSPD5) that converts glycerol to 1,3-propanediol. This two-step strategy led to a flexible process, resulting in a 1,3-propanediol production and yield that depended on the initial sugar concentration. Below 56.2 g l−1 of sugar concentration, cultivation on molasses or glucose showed no significant differences. However, at higher molasses concentrations, glycerol initially produced by yeast could not be totally converted into 1,3-propanediol by C. acetobutylicum and a lower 1,3-propanediol overall yield was observed. In our hand, the best results were obtained with an initial glucose concentration of 103 g l−1, leading to a final 1,3-propanediol concentration of 25.5 g l−1, a productivity of 0.16 g l−1 h−1 and 1,3-propanediol yields of 0.56 g g−1 glycerol and 0.24 g g−1 sugar, which is the highest value reported for a two-step process. For an initial sugar concentration (from molasses) of 56.2 g l−1, 27.4 g l−1 of glycerol were produced, leading to 14.6 g l−1 of 1.3-propanediol and similar values of productivity, 0.15 g l−1 h−1, and overall yield, 0.26 g g−1 sugar.
- Alcohols, esters and heavy sulphur compounds production by pure and mixed cultures of apiculate wine yeastsPublication . Moreira, Nathalie; Mendes, Filipa; Hogg, Tim; Vasconcelos, IsabelStrains of Hanseniaspora uvarum, Hanseniaspora guilliermondii and Saccharomyces cerevisiae were used as pure or mixed starter cultures in commercial medium, in order to compare their kinetic parameters and fermentation patterns. In pure and mixed cultures, yeasts presented similar ethanol yield and productivity. Pure cultures of H. uvarum and S. cerevisiae showed a specific growth rate of 0.38 h⁻¹; however, this value decreased when these yeasts were grown in mixed cultures with H. guilliermondii. The specific growth rate of pure cultures of H. guilliermondii was 0.41 h⁻⁻¹ and was not affected by growth of other yeasts. H. guilliermondii was found to be the best producer of 2-phenylethyl acetate and 2-phenylethanol in both pure and mixed cultures. In pure cultures, H. uvarum led to the highest contents of heavy sulphur compounds, but H. guilliermondii and S. cerevisiae produced similar levels of methionol and 2-methyltetrahydrothiophen-3-one. Growth of apiculate yeasts in mixed cultures with S. cerevisiae led to amounts of 3-methylthiopropionic acid, acetic acid-3-(methylthio)propyl ester and 2- methyltetrahydrothiophen-3-one similar to those obtained in a pure culture of S. cerevisiae; however, growth of apiculate yeasts increased methionol contents of fermented media.
- Characterizing the potential of the non-conventional yeast Saccharomycodes ludwigii UTAD17 in winemakingPublication . Esteves, Marcos; Barbosa, Catarina; Vasconcelos, Isabel; Tavares, Maria João; Mendes-Faia, Arlete; Mira, Nuno Pereira; Mendes-Ferreira, AnaNon-Saccharomyces yeasts have received increased attention by researchers and winemakers, due to their particular contributions to the characteristics of wine. In this group, Saccharomycodes ludwigii is one of the less studied species. In the present study, a native S. ludwigii strain, UTAD17 isolated from the Douro wine region was characterized for relevant oenological traits. The genome of UTAD17 was recently sequenced. Its potential use in winemaking was further evaluated by conducting grape-juice fermentations, either in single or in mixed-cultures, with Saccharomyces cerevisiae, following two inoculation strategies (simultaneous and sequential). In a pure culture, S. ludwigii UTAD17 was able to ferment all sugars in a reasonable time without impairing the wine quality, producing low levels of acetic acid and ethyl acetate. The overall effects of S. ludwigii UTAD17 in a mixed-culture fermentation were highly dependent on the inoculation strategy which dictated the dominance of each yeast strain. Wines whose fermentation was governed by S. ludwigii UTAD17 presented low levels of secondary aroma compounds and were chemically distinct from those fermented by S. cerevisiae. Based on these results, a future use of this non-Saccharomyces yeast either in monoculture fermentations or as a co-starter culture with S. cerevisiae for the production of wines with greater expression of the grape varietal character and with flavor diversity could be foreseen. View Full-Text
- Combined effects of nitrogen availability and co-fermentation with hanseniaspora guillermondii on wine aroma profilePublication . Lage, P.; Barbosa, C.; Mateus, B.; Vasconcelos, Isabel; Mendes-Faia, A.; Mendes-Ferreira, A.
- Continuous cultures of Clostridium acetobutylicum: culture stability and low-grade glycerol utilisationPublication . Andrade, José Carlos; Vasconcelos, IsabelContinuous cultures of two strains of Clostridium acetobutylicum were stable for over 70 d when grown on glucose/ glycerol mixtures. Butanol was the major fermentation end-product, accounting for 43 to 62% (w/w) of total products. Low-grade glycerol [65% (w/v) purity] could replace commercial glycerol [87% (w/v) purity], leading to a similar fermentation pattern: a butanol yield of 0.34 (mol/mol), a butanol productivity of 0.42 g l−1 h−1 and a 84% (w/w) glycerol consumptionwere attained when cultures were grown at pH 6 and D = 0.05 h−1; butanol accounted for 94% (w/w) of total solvents. These values are among the highest reported in literature for C. acetobutylicum simple chemostats.
- Development and optimization of a HS-SPME-GC-MS methodology to quantify volatile carbonyl compounds in Port winesPublication . Moreira, Nathalie; Araújo, Ana Margarida; Rogerson, Frank; Vasconcelos, Isabel; Freitas, Victor de; Pinho, Paula Guedes deA method based on headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-triple quadrupole/mass spectrometry detection (GC-TQ/MS) with a prior derivatization step with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) was developed to quantify carbonyl compounds in different categories of Port wines. Optimal extraction conditions were obtained incubating 2 ml of wine with 2.3 g/l of PFBHA for 10 min and extracted during 20 min at 32 °C. The method was validated for 38 carbonyl compounds (alkanals, alkenals, Strecker aldehydes, dialdehydes, ketones and furan aldehydes) with regard to linearity, repeatability, inter and intra-day precision and accuracy, showing that the method is suitable for the determination of carbonyl compounds in wines. Tawny wines with ‘indication of age’ (10–40 years old) presented the highest levels of some carbonyl compounds, such as propanal, pentanal, hexanal, Strecker aldehydes, diacetyl, methyl glyoxal, 3-pentanone and 2-furfural, whereas Ruby wines were characterized by the highest amounts of some unidentified compounds.
- Effect of skin contact and oxygenation of muts on the composition of white port winesPublication . Ho, Peter; Rogerson, Frank S.S.; Watkins, Steve J.; Silva, Maria da Conceição M.; Hogg, Tim; Vasconcelos, IsabelWhite port wine were made from Malvaela Fina and Rabigata gaps musts that were subjected to different combinations of skin contact and must oxygenation. Increasing skin contact times increased the total phenolics. Total hydroxycinnamoyl tartaric acid, total flavonoids and the formation of brown pigments in the tree-run musts. Both air exposure and hyperoxidation were effective in lowering the concentration of hydroxycinnamoyl tartaric acids and flavonoids it newly fermented wines. Hyperoxidation seemed more effective in removing this phenolic compounds and U1 reducing browning than air expo- sure In wines which had 8 and 25 h of akin contact. Phenolic compounds increased with wood ageing. Although the concentration of hydroxycinnamic acide were lower In all oxygenated wines than in the controls. However must oxygenation prior to fermentation could not prevent further browning of the wines, caused by the production of furans and the increase of flavonoids during that ageing it wood. increasing skin contact generally increased the total monoterpene alcohol concentration for hyperoxidised whesm with some increases it air exposed wines. Total monoterpene alcohol concentration was higher Hyperoxidised than in air exposed wines, made from musts with 8 and 25h of skin contact, after 18 months of wood ageing.
- H. guilliermondii impacts growth kinetics and metabolic activity of s. cerevisiae: the role of initial nitrogen concentrationPublication . Lage, Patrícia; Barbosa, Catarina; Mateus, Beatriz; Vasconcelos, Isabel; Mendes-Faia, Arlete; Mendes-Ferreira, AnaNon-Saccharomyces yeasts include different species which comprise an ecologically and biochemically diverse group capable of altering fermentation dynamics and wine composition and flavour. In this study, single- and mixed-culture of Hanseniaspora guilliermondii and Saccharomyces cerevisiae were used to ferment natural grape-juice, under two nitrogen regimes. In single-culture the strain H. guilliermondii failed to complete total sugar breakdown even though the nitrogen available has not been a limiting factor of its growth or fermentative activity. In mixed-culture, that strain negatively interfered with the growth and fermentative performance of S. cerevisiae, resulting in lower fermentation rate and longer fermentation length, irrespective of the initial nitrogen concentration. The impact of co-inoculation on the volatile compounds profilewasmore evident in thewines obtained from DAP-supplementedmusts, characterised by increased levels of ethyl and acetate esters, associated with fruity and floral character of wines. Moreover, the levels of fatty acids and sulphur compounds which are responsible for unpleasant odours that depreciate wine sensory quality were significantly lower. Accordingly, data obtained suggests that the strain H. guilliermondii has potential to be used as adjunct of S. cerevisiae in wine industry, although possible interactions with S. cerevisiae still need to be elucidated.
- Insights into the transcriptional regulation of poorly characterized alcohol acetyltransferase-encoding genes (HgAATs) shed light into the production of acetate esters in the wine yeast Hanseniaspora guilliermondiiPublication . Seixas, Isabel; Santos, Diogo; Vasconcelos, Isabel; Mira, Nuno P.; Mendes-Ferreira, AnaHanseniaspora guilliermondii is a well-recognized producer of acetate esters associated with fruity and floral aromas. The molecular mechanisms underneath this production or the environmental factors modulating it remain unknown. Herein, we found that, unlike Saccharomyces cerevisiae, H. guilliermondii over-produces acetate esters and higher alcohols at low carbon-to-assimilable nitrogen (C:N) ratios, with the highest titers being obtained in the amino acid-enriched medium YPD. The evidences gathered support a model in which the strict preference of H. guilliermondii for amino acids as nitrogen sources results in a channeling of keto-acids obtained after transamination to higher alcohols and acetate esters. This higher production was accompanied by higher expression of the four HgAATs, genes, recently proposed to encode alcohol acetyl transferases. In silico analyses of these HgAat's reveal that they harbor conserved AATs motifs, albeit radical substitutions were identified that might result in different kinetic properties. Close homologues of HgAat2, HgAat3, and HgAat4 were only found in members of Hanseniaspora genus and phylogenetic reconstruction shows that these constitute a distinct family of Aat's. These results advance the exploration of H. guilliermondii as a bio-flavoring agent providing important insights to guide future strategies for strain engineering and media manipulation that can enhance production of aromatic volatiles.
- Lowering costs of microbial cellulosePublication . Pajuelo, María González; Bungay, Henry; Hogg, Tim; Vasconcelos, IsabelWe have been conducting research with Acetobacter xylinium for microbial conversion of sugars to cellulose. A rotating disk biological contactor should lower costs considerably because its production rates are greater than for the usual method of surface culture. Another major cost saving comes from replacing expensive sugars in the medium with sugars derived from wastes. Extracts of spent grapes from wastes of Portuguese wine factories supply suitable sugars for good production of microbial cellulose.
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