Aromatic Amino Acid-Derived Compounds Induce Morphological Changes and Modulate the Cell Growth of Wine Yeast Species.

Beatriz González,María-Jesús Torija,Albert Mas,Gemma Beltran,Paul J Cullen,Jennifer Vázquez

doi:10.3389/fmicb.2018.00670

Abstract

Yeasts secrete a large diversity of compounds during alcoholic fermentation, which affect growth rates and developmental processes, like filamentous growth. Several compounds are produced during aromatic amino acid metabolism, including aromatic alcohols, serotonin, melatonin, and tryptamine. We evaluated the effects of these compounds on growth parameters in 16 different wine yeasts, including non-Saccharomyces wine strains, for which the effects of these compounds have not been well-defined. Serotonin, tryptamine, and tryptophol negatively influenced yeast growth, whereas phenylethanol and tyrosol specifically affected non-Saccharomyces strains. The effects of the aromatic alcohols were observed at concentrations commonly found in wines, suggesting a possible role in microbial interaction during wine fermentation. Additionally, we demonstrated that aromatic alcohols and ethanol are able to affect invasive and pseudohyphal growth in a manner dependent on nutrient availability. Some of these compounds showed strain-specific effects. These findings add to the understanding of the fermentation process and illustrate the diversity of metabolic communication that may occur among related species during metabolic processes.

Highlights

Wine is produced by alcoholic fermentation, in which grape sugars are metabolized into ethanol by yeast
To evaluate the effects of amino acid-derived compounds on yeast growth, five strains of S. cerevisiae and one strain of each non-Saccharomyces species were grown in the presence of 1000 mg/L of Mel, Ser, Trpm, TyrOH, PheOH, or TrpOH
As these molecules are derived from nitrogen metabolism, and quorum sensing molecules (QSMs) are produced during nutrient limitation, we tested their effects under two different nitrogen conditions: 1 and 10 mM (NH4)2SO4 (Figure 1)

Summary

Introduction

Wine is produced by alcoholic fermentation, in which grape sugars are metabolized into ethanol by yeast. Microorganisms belonging to the Saccharomyces genus are present in low abundance and are difficult to detect in initial must (Ribéreau-Gayon et al, 2006) For this reason, during spontaneous fermentation, non-Saccharomyces yeasts are responsible for initiating alcoholic fermentation and are out-competed by S. cerevisiae throughout fermentation (Heard and Fleet, 1988; Fleet, 2003; Ribéreau-Gayon et al, 2006). The importance of non-Saccharomyces strains in alcoholic fermentation has Aromatic Alcohol Effects on Wine Yeast become appreciated, in terms of their contribution to wine aroma, during the early steps of fermentation These species have been reported to impact, sometimes positively, winemaking via the production of high amounts of aromatic compounds, such as aromatic alcohols, ethyl esters, and acetate esters (Romano et al, 2003; García et al, 2010; Jolly et al, 2014; Belda et al, 2017). These strains appear to be present throughout much of the fermentation process, this finding has been neglected because such strains are difficult to culture (Millet and Lonvaud-Funel, 2000; Wang et al, 2015a, 2016)

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