Loading...
65 results
Search Results
Now showing 1 - 10 of 65
- 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.
- 1,3-Propanediol continuous production by Clostridium butyricum VP1 1718: effect of dilution rate and substrate concentrationPublication . Gonzalez-Pajuelo, M.; Ribeiro-Cruz, A. P.; Sousa- Monagas, C. M.; Andrade, J. C.; Vasconcelos, I.
- Effet de la souche de levure sur les proprietes organoleptiques des vins issus de cinq cepages blancs portugaisPublication . Vasconcelos, I.; Moura, F.; Martins, M. C. P.; Herdeiro, M. T.; Pereira, O.; Castro, A.; Revel, G. deNeuf souches de levures commerciales, appartenant au genre Saccharomyces (six souches de S. cerevisiae et trois souches de S. bayanus), ont ete testees lors de la fermentation de moths issus de cinq cepages portugais: Loureiro, Trajadura, Pedernk Azal e Avesso. Pour un même cepage la levure d'implantation semble ne pas avoir d'influence sur la teneur en alcool et sur l'acidité totale des vins produits. Les variations des quantites produites en esters ethyliques d'acides gras (BRAG) et acetates d'alcools superieurs (AAS) peuvent varier d'un facteur 2.1 et 4.3 respectivement, pour un même cepages les teneurs maximales en AAS sont observêes avec les deux mêmes souches pour tour les cepages, a une exception pres. En ce qui concerne les alcools superieurs, les souches plus ou moths productrices different pour chaque cépage. Une etude statistique a permis d'etablir une correlation entre l'analyse chimique et l'analyse sensorielle. D'un point de vue organoleptique, les vins prefer-es sont riches en acides gras et en EEAG mais relativement pauvres en AAS.
- Unveiling the role of the elusive HgAATs in ester production by Hanseniaspora guilliermondiiPublication . Seixas, Isabel; Vasconcelos, Isabel; Mira, Nuno; Mendes-Ferreira, Ana
- Apiculate wine yeasts: growth kinetics and aroma compounds productionPublication . Moreira, N. E. O.; Silva, C. L. M.; Vasconcelos, I. M.; Mendes, F.; Hogg, T.
- Production of 1,3-propanediol by Clostridium butyricum VPI 3266 using a synthetic medium and raw glycerolPublication . González-Pajuelo, M.; Andrade, J. C.; Vasconcelos, I.Growth inhibition of Clostridium butyricum VPI 3266 by raw glycerol, obtained from the biodiesel production process, was evaluated. C. butyricum presents the same tolerance to raw and to commercial glycerol, when both are of similar grade, i.e. above 87% (w/v). A 39% increase of growth inhibition was observed in the presence of 100 g l 1 of a lower grade raw glycerol (65% w/v). Furthermore, 1,3-propanediol production from two raw glycerol types (65% w/v and 92% w/v), without any prior purification, was observed in batch and continuous cultures, on a synthetic medium. No significant differences were found in C. butyricum fermentation patterns on raw and commercial glycerol as the sole carbon source. In every case, 1,3-propanediol yield was around 0.60 mol/mol glycerol consumed.
- Relationship between nitrogen content in grape volatiles, namely heavy sulphur compounds, in winesPublication . Moreira, Nathalie; Pinho, Paula Guedes de; Santos, Cristina; Vasconcelos, IsabelAmmonium salts were added to white grape musts, before alcoholic fermentation, in order to evaluate their influence on the heavy sulphur compound and aliphatic higher alcohol composition of resulting wines. Six grape musts were used (Trajadura, Pedernã, Loureiro, Azal Branco, Avesso and Alvarinho). Ammonium supplementation of Trajadura and Pedernã grape musts, with the highest nitrogen level, did not influence the content of heavy sulphur compounds and aliphatic higher alcohols in wines; however, the addition of ammonium salts to grape musts with low initial nitrogen content, such as Loureiro, Azal Branco and Avesso, led to a higher production of 1-propanol and a lower production of isoamyl alcohols and sulphur compounds, e.g. S-methyl thioacetate, 2-mercaptoethanol, acetic acid-3-(methylthio)propyl ester, 3-mercapto-1-propanol, 4-(methylthio)-1-butanol, 3-(ethyithio)-1-propanol. 3-methylthiopropionic acid and N-3-(methylthiopropyl)acetamide. For Alvarinho grape must, a decrease in sulphur compound concentrations in wines was only observed for 3-methylthiopropionic acid, acetic acid-3-(methylthio)propyl ester and 2-mercaptoethanol.
- 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
- Medição da densidade na fermentação de vinhos através da dinâmica térmica do processoPublication . Moreira, A. Paulo G. M.; Carvalho, J. L. Martins de; Hoog, Tim; Vasconcelos, Isabel
- 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.