The production of volatile metabolic products was determined for five Brettanomyces bruxellensis isolates from wine when grown in a defined medium with and without the hydroxycinnamic acids caffeic, coumaric, and ferulic or the aromatic amino acids phenylalanine, tryptophan, and tyrosine. The aim of the study was to determine the relationship between substrates and end products and to define strain differences in the production of volatile compounds. In the presence of coumaric and ferulic acids, all strains produced very similar metabolic products, primarily 4-ethylphenol (4EP) and 4-ethylguaiacol (4EG), respectively. There was a more pronounced effect of strain with the other substrates, and a variety of compounds with the potential to impact wine aroma were detected. Growth of Brettanomyces in the defined medium, with and without coumaric acid, under varying oxygen concentrations was also studied to determine the effect of this compound on growth parameters. The highest concentrations of 4EP were found under anaerobic conditions. Coumaric acid also had a significant positive affect on growth of Brettanomyces at 25% air saturation levels. At full aeration, coumaric acid addition showed little to no impact on growth or 4EP formation. Significantly higher concentrations of acetic acid were formed in the presence of coumaric acid, suggesting that 4EP formation may aid in the recycling of oxidized cofactor NAD+.
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