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Combined effects of nitrogen availability and co-fermentation with hanseniaspor...

" Pesquisa de mercúrio e outros metais em dentes restaurados a amálgama pelo mé...

Mestrado em Medicina Legal ; Master Degree in Forensic Medicine

1,3-Propanediol production in a two-step process fermentation from renewable fe...

In 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 perfo...

Relationship between nitrogen content in grape volatiles, namely heavy sulphur ...

Ammonium 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 ...

Volatile sulphur compounds composition of monovarietal white wines

The sulphur compounds composition of wines produced experimentally from six white cultivars (Alvarinho, Loureiro, Trajadura, Pedernã, Azal Branco and Avesso) was evaluated during two consecutive vintages. Results show that wines could be differentiated according to their sulphur compounds content. In general, Loureiro, Trajadura and Pedernã cultivars led to wines with low concentrations of sulphur compounds; ho...

Sequential injection kinetic flow assay for monitoring glycerol in a sugar ferm...

A sequential injection system to monitor glycerol in a Saccharomyces cerevisiae fermentation process was developed. The method relies on the rate of formation of nicotinamide adenine dinucleotide in its reduced form (NADH, measured spectrophotometrically at 340 nm) from the reaction of glycerol with NAD+ cofactor, catalysed by the enzyme glycerol dehydrogenase present in solution. This procedure enables the de...

Microbial conversion of glycerol to 1,3-propanediol$ephysiological comparison o...

Clostridium acetobutylicum is not able to grow on glycerol as the sole carbon source since it cannot reoxidize the excess of NADH generated by glycerol catabolism. Nevertheless, when the pSPD5 plasmid, carrying the NADH-consuming 1,3-propanediol pathway from C. butyricum VPI 3266, was introduced into C. acetobutylicum DG1, growth on glycerol was achieved, and 1,3-propanediol was produced. In order to compare th...

Metabolic engineering of clostridium acetobutylicum for the industrial producti...

Clostridium butyricum is to our knowledge the best natural 1,3-propanediol producer from glycerol and the only microorganism identified so far to use a coenzyme B12-independent glycerol dehydratase. However, to develop an economical process of 1,3-propanediol production, it would be necessary to improve the strain by a metabolic engineering approach. Unfortunately, no genetic tools are currently available for C...

Alcohols, esters and heavy sulphur compounds production by pure and mixed cultu...

Strains 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, thi...

Continuous cultures of Clostridium acetobutylicum: culture stability and low-gr...

Continuous 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 pro...