Modulation of Aromatic Amino Acid Metabolism by Indigenous Non-Saccharomyces Yeasts in Croatian Maraština Wines

This study aimed to provide novel information on the impact of indigenous non-<i>Saccharomyces yeasts</i>, including <i>Metschnikowia chrysoperlae</i>, <i>Metschnikowia sinensis</i>/<i>shanxiensis</i>, <i>Metschnikowia pulcherrima</i>, <i>Lachancea thermotolerans</i>, <i>Hanseniaspora uvarum</i>, <i>Hanseniaspora guilliermondii</i>, and <i>Pichia kluyveri</i>, on metabolites related to the metabolism of tryptophan, phenylalanine, and tyrosine. The experiment included two fermentation practices: monoculture and sequential fermentation with commercial <i>Saccharomyces cerevisiae</i>, using sterile Maraština grape juice. A targeted approach through ultrahigh-resolution liquid chromatography associated with mass spectrometry was used to quantify 38 metabolites. All the indigenous yeasts demonstrated better consumption of tryptophan in monoculture than in interaction with <i>S. cerevisiae</i>. <i>M. sinensis</i>/<i>shanxiensis</i> was the only producer of indole-3-carboxylic acid, while its ethyl ester was detected in monoculture fermentation with <i>H. guilliermondii</i>. <i>H. guilliermondii</i> consumed the most phenylalanine among the other isolates. 5-hydroxy-L-tryptophan was detected in fermentations with <i>M. pulcherrima</i> and <i>M. sinensis</i>/<i>shanxiensis</i>. <i>M. pulcherrima</i> significantly increased tryptophol content and utilised tyrosine in monoculture fermentations. Sequential fermentation with <i>M. sinensis</i>/<i>shanxiensis</i> and <i>S. cerevisiae</i> produced higher amounts of N-acetyl derivatives of tryptophan and phenylalanine, while <i>H. guilliermondii</i>-<i>S. cerevisiae</i> fermentation resulted in wines with the highest concentrations of L-kynurenine and 3-hydroxyanthranilic acid. <i>P. kluyveri</i> produced the highest concentration of N-acetyl-L-tyrosine in monoculture fermentations. These findings highlight the different yeast metabolic pathways.