1 research outputs found
<i>De Novo</i> Synthesis of Benzenoid Compounds by the Yeast <i>Hanseniaspora vineae</i> Increases the Flavor Diversity of Wines
Benzyl alcohol and
other benzenoid-derived metabolites of particular
importance in plants confer floral and fruity flavors to wines. Among
the volatile aroma components in <i>Vitis vinifera</i> grape
varieties, benzyl alcohol is present in its free and glycosylated
forms. These compounds are considered to originate from grapes only
and not from fermentative processes. We have found increased levels
of benzyl alcohol in red Tannat wine compared to that in grape juice,
suggesting <i>de novo</i> formation of this metabolite during
vinification. In this work, we show that benzyl alcohol, benzaldehyde, <i>p</i>-hydroxybenzaldehyde, and <i>p</i>-hydroxybenzyl
alcohol are synthesized <i>de novo</i> in the absence of
grape-derived precursors by <i>Hanseniaspora vineae</i>.
Levels of benzyl alcohol produced by 11 different <i>H. vineae</i> strains were 20–200 times higher than those measured in fermentations
with <i>Saccharomyces cerevisiae</i> strains. These results
show that <i>H. vineae</i> contributes to flavor diversity
by increasing grape variety aroma concentration in a chemically defined
medium. Feeding experiments with phenylalanine, tryptophan, tyrosine, <i>p</i>-aminobenzoic acid, and ammonium in an artificial medium
were tested to evaluate the effect of these compounds either as precursors
or as potential pathway regulators for the formation of benzenoid-derived
aromas. Genomic analysis shows that the phenylalanine ammonia-lyase
(<i>PAL</i>) and tyrosine ammonia lyase (<i>TAL</i>) pathways, used by plants to generate benzyl alcohols from aromatic
amino acids, are absent in the <i>H. vineae</i> genome.
Consequently, alternative pathways derived from chorismate with mandelate
as an intermediate are discussed