Isotopic Tracers Unveil Distinct Fates for Nitrogen Sources during Wine Fermentation with Two Non-Saccharomyces Strains.

Anne Ortiz-Julien,José Manuel Guillamón,Carole Camarasa,José María Heras,Audrey Bloem,Pauline Seguinot,Ying Su

doi:10.3390/microorganisms8060904

Abstract

Non-Saccharomyces yeast strains have become increasingly prevalent in the food industry, particularly in winemaking, because of their properties of interest both in biological control and in complexifying flavour profiles in end-products. However, unleashing the full potential of these species would require solid knowledge of their physiology and metabolism, which is, however, very limited to date. In this study, a quantitative analysis using 15N-labelled NH4Cl, arginine, and glutamine, and 13C-labelled leucine and valine revealed the specificities of the nitrogen metabolism pattern of two non-Saccharomyces species, Torulaspora delbrueckii and Metschnikowia pulcherrima. In T. delbrueckii, consumed nitrogen sources were mainly directed towards the de novo synthesis of proteinogenic amino acids, at the expense of volatile compounds production. This redistribution pattern was in line with the high biomass-producer phenotype of this species. Conversely, in M. pulcherrima, which displayed weaker growth capacities, a larger proportion of consumed amino acids was catabolised for the production of higher alcohols through the Ehrlich pathway. Overall, this comprehensive overview of nitrogen redistribution in T. delbrueckii and M. pulcherrima provides valuable information for a better management of co- or sequential fermentation combining these species with Saccharomyces cerevisiae.

Highlights

Wine fermentation is a process in which sugars are converted into ethanol through interactions between microorganisms, mainly yeast species, imparting pleasant notes to wines [1]
As previously reported for S. cerevisiae, consumed nitrogen sources were mainly catabolised for the de novo synthesis of amino acids, arginine, and to a lesser extent histidine and lysine, were mainly incorporated directly into proteins
Differences between strains were observed, as T. delbrueckii used ammonium preferentially to glutamine, while ammonium incorporation was low in M. pulcherrima

Summary

Introduction

Wine fermentation is a process in which sugars are converted into ethanol through interactions between microorganisms, mainly yeast species, imparting pleasant notes to wines [1]. Two of the most studied and commercialised of these species are Torulaspora delbrueckii and Metschnikowia pulcherrima [6], used to reduce the production of ethanol and volatile acids while, on the contrary, increasing glycerol concentration and wine aromatic complexity (for a review see [7], and references therein). Due to their low tolerance to ethanol or SO2, non-Saccharomyces yeasts are unable to consume all the sugars available in grape juices, and are often used together with S. cerevisiae in co- or sequential fermentations to ensure complete wine fermentation. Understanding nitrogen metabolism during fermentation is of utmost significance

Objectives

Methods

Results

Discussion

Conclusion