Nitrogen sources preferences of non-Saccharomyces yeasts to sustain growth and fermentation under winemaking conditions

Abstract

Wine-related non-Saccharomyces yeasts are becoming more widely used in oenological practice for their ability to confer wine a more complex satisfying aroma, but their metabolism remains unknown. Our study explored the nitrogen utilisation profile of three popular non-Saccharomyces species, Torulaspora delbrueckii, Metschnikowia pulcherrima and Metschnikowia fructicola. The nitrogen source preferences to support growth and fermentation as well as the uptake order of different nitrogen sources during wine fermentation were investigated. While T. delbrueckii and S. cerevisiae strains shared the same nitrogen source preferences, Metschnikowia sp. displayed a lower capacity to efficiently use the preferred nitrogen compounds, but were able to assimilate a wider range of amino acids. During alcoholic fermentation, the non-Saccharomyces strains consumed different nitrogen sources in a similar order as S. cerevisiae, but not as quickly. Furthermore, when all the nitrogen sources were supplied in the same amount, their assimilation order was similarly affected for both S. cerevisiae and non-Saccharomyces strains. Under this condition, the rate of nitrogen source consumption of non-Saccharomyces strains and S. cerevisiae was comparable. Overall, this study expands our understanding about the preferences and consumption rates of individual nitrogen sources by the investigated non-Saccharomyces yeasts in a wine environment. This knowledge provides useful information for a more efficient exploitation of non-Saccharomyces strains that improves the management of the wine fermentation.

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

“…As a general rule, the lag phase of sequential fermentation during which M. pulcherrima was the only yeast in the medium was shorter than that of S. cerevisiae pure culture. This result was consistent with previous findings indicating a shorter lag phase for M. pulcherrima (Su et al, 2020). The changes in the lag phase duration in response to changes in nutrient availability were similar for both strains.…”

“…In fact, when nitrogen was limiting (80 mg/L), the substantial consumption of nitrogen sources during the M. pulcherrima pure culture stage, up to 80% of the provided YAN, prevented the further implantation of S. cerevisiae, leading to a slow-down of fermentation. In the case of moderate and high initial YAN contents, the residual nitrogen level was higher at the time of S. cerevisiae addition, between 95 and 190 mg N/L, but some specific nitrogen sources, such as branched amino acids, glutamate and glutamine, were exhausted, in accordance with the sequence of the consumption of nitrogen sources by M. pulcherrima previously reported by Su et al (2020). As a consequence, the nitrogen resources available to promote further S. cerevisiae implantation were mainly composed of proline, tryptophan, glycine and alanine, which support the growth and fermentation of the yeast poorly (Godard et al, 2007;Fairbairn et al, 2017).…”

Nitrogen Preferences during Alcoholic Fermentation of Different Non-Saccharomyces Yeasts of Oenological Interest

“…These results do not agree with Prior et al [33], who reported no difference in amino acids' uptake in L. thermotolerans or T. delbrueckii, with and without ammonium. Under this condition, the latest amino acid consumed by T. delbrueckii and L. thermotolerans was glycine, which has been previously described as a poor nitrogen source for several yeast species [12,32,35,56,57]. Indeed, glycine was also one of the less preferred amino acids for M. pulcherrima and S. bacillaris, being even excreted/produced by M. pulcherrima in SM-Mix.…”

“…While nitrogen consumption and preferences are well researched in S. cerevisiae [17,[23][24][25][26][27][28][29][30][31], nutrient uptake by non-Saccharomyces yeasts has not been extensively studied. Available studies have analyzed the preferential nitrogen sources of some non-Saccharomyces yeasts, focusing on their capacity to assimilate different nitrogen compounds, their rate of consumption, or their influence in aroma production [2,19,[32][33][34][35][36][37][38]. The firsts studies reported that the nitrogen sources directly affect the fermentation performance and yeast growth in a species-specific manner [32,39].…”

“…The firsts studies reported that the nitrogen sources directly affect the fermentation performance and yeast growth in a species-specific manner [32,39]. Later, some studies have revealed that non-Saccharomyces yeasts have specific profiles for amino acid consumption, concluding that the different nitrogen composition of the media strongly influences the assimilation order of each compound, both in natural [19] and synthetic must [12,35,37]. Different studies have analyzed the possible competition for nutrients between Saccharomyces and non-Saccharomyces yeasts [11,12,[40][41][42].…”