Caracterização da conversão metabólica de ácidos fenólicos em fenóis voláteis por Brettanomyces/Dekkera

Abstract

The accumulation of volatile phenols in wine has been a cause of great concern in modern enology, being considered, nowadays, a key point in the control of wine quality. Vinylphenols (4-vinylphenol and 4 vinylguaiacol) and ethylphenols (4- ethylphenol and 4-ehtylguaiacol) may be produced in wine, in a sequence pathway, due to microbial activity, imparting undesirable odours and flavours commonly described as “leather”, “horse sweat”, “animal” and “medicinal”. The precise origin(s) of volatile phenols has been under discussion for some time. The production of these compounds has been recognised as an important characteristic of the yeast Brettanomyces/Dekkera. It is aimed in this work to characterize growth and metabolic activity of Brettanomyces/Dekkera in particular as regards the activity of the enzymes hidroxicinamato decarboxylase and vinylphenol reductase using different precursors for the production of 4-ethylphenol. It was identified that the p-coumaric acid and phloretic acid have no significant influence on the growth of D. bruxellensis and D. anomala. The enzyme hidroxicinamate decarboxylase showed specificity towards precursors with a double bond at the carboxylic group (hydroxycinnamic acids). The position of the substituent - OH group also shown to have influence on the functioning of the enzyme and subsequent production of 4-ethylphenol. Phloretic acid was metabolized but not in 4- ethylphenol. All tested strains converted p-coumaric acid and vinylphenol to 4- ethylphenol, although to different extents.

Date of Award	2012
Original language	Portuguese
Awarding Institution	Universidade Católica Portuguesa
Supervisor	José António Couto (Supervisor) & Francisco Campos (Co-Supervisor)