Impact of Nutrient Availability on the Fermentation and Production of Aroma Compounds Under Sequential Inoculation With M. pulcherrima and S. cerevisiae

Abstract

Non-Saccharomyces yeasts are currently widely used in winemaking to enhance aroma profile diversity among wines. The use of Metschnikowia pulcherrima in sequential inoculation with S. cerevisiae was compared to the inoculation of a pure culture of S. cerevisiae. Moreover, various concentrations of sugar, nitrogen and lipids were tested in synthetic must to assess their impact on fermentation and its outcomes using a Box-Behnken design. Due to its phenotypic specificities, early inoculation with M. pulcherrima led to important modifications, first altering the fermentation kinetics. This may relate, at least in part, to the depletion of some nitrogen sources by M. pulcherrima during the first part of fermentation. Beyond these negative interactions on fermentation performance, comparisons between pure cultures and sequentially inoculated cultures revealed changes in the distribution of carbon fluxes during fermentation in presence of M. pulcherrima, resulting in a positive impact on the production of central carbon metabolites and aromas. Furthermore, the expression of varietal thiols was strongly increased as a consequence of positive interactions between the two species. The mechanism of this release still needs to be investigated. Significant differences in the final concentrations of fermentative and varietal aromas depending on the initial must composition were obtained under both inoculation strategies. Interestingly, the response to changes in nutrient availability varied according to the inoculation modality. In particular, a greater incidence of lipids on the production of fatty acids and their ethyl esters derivatives was found during sequential fermentation compared with pure culture, to be viewed in combination with the metabolic characteristics of M. pulcherrima regarding the production of volatile compounds from acetyl-CoA. Overall, the importance of managing nutrient availability under M. pulcherrima/S. cerevisiae sequential inoculation in order to derive the maximum benefit from the potentialities of the non-Saccharomyces species while carrying out fermentation to dryness was highlighted.

Effect of a Multistarter Yeast Inoculum on Ethanol Reduction and Population Dynamics in Wine Fermentation

“…Moreover, the relative proportion between yeast species during the fermentation could affect the metabolite production. Indeed, comparisons between pure cultures and sequentially inoculated cultures revealed changes in the distribution of carbon fluxes during fermentation [ 78 ]. Finally, the initial must composition and nutrient availability can also have an impact in the metabolite production, as previously demonstrated by Seguinot et al [ 78 ].…”

“…Non- Saccharomyces yeasts usually differ from S. cerevisiae in the distribution of their metabolic flux during fermentation [ 46 , 67 , 78 , 80 ]. Indeed, several non- Saccharomyces species are able to aerobically respire sugar, which results in altered formation of the main metabolites produced during fermentation, including ethanol, glycerol and organic acids [ 3 , 20 , 45 , 46 ].…”

The Genus Metschnikowia in Enology

“…During sequential fermentation with M. pulcherrima and S. cerevisiae , adequate management of yeast nutrition is essential, especially regarding the nitrogen source. The addition of nitrogen at the moment of S. cerevisiae inoculation is recommended for facilitating the completion of the fermentative process [ 51 ]. M. pucherrima sequential fermentations seems to increase the final amino acid concentration in wine.…”

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

“…It may be explained by a deficit in this strain in acetyl-CoA, which is used as co-substrate in the first step of the conversion of α-ketoisovalerate into α-ketoisocaproate by LEU4 and LEU9 [ 43 ]. We had already assumed that the intracellular availability of acetyl-CoA was limited in this strain, because of its low ability to produce acetate, acetate esters, and medium-chain fatty acids and their ethyl ester derivatives [ 44 ].…”