Diversity and dynamics of fungi during spontaneous fermentations and association with unique aroma profiles in wine

Abstract

Microbial activity is an integral part of an agricultural ecosystem and influences the quality of agricultural commodities. Microbial ecology influences grapevine health and crop production, conversion of sugar to ethanol during fermentation, thus wine aroma and flavour. There are regionally differentiated microbial patterns in grapevines and must but how microbial patterns contribute to wine regional distinctiveness (terroir) at small scale (<100 km) is not well defined. Here we characterise fungal communities, yeast populations, and Saccharomyces cerevisiae populations during spontaneous fermentation using metagenomics and population genetics to investigate microbial distribution and fungal contributions to the resultant wine. We found differentiation of fungi, yeasts, and S. cerevisiae between geographic origins (estate/vineyard), with influences from the grape variety. Growth and dominance of S. cerevisiae during fermentation reshaped the fungal community and showed geographic structure at the strain level. Associations between fungal microbiota diversity and wine chemicals suggest that S. cerevisiae plays a primary role in determining wine aroma profiles at a sub-regional scale. The geographic distribution at scales of less than 12 km supports that differential microbial communities, including the dominant fermentative yeast S. cerevisiae can be distinct in a local setting. These findings provide further evidence for microbial contributions to wine terroir, and perspectives for sustainable agricultural practices to maintain microbial diversity and optimise fermentation function to craft beverage quality.

Wine phenolic profile altered by yeast: Mechanisms and influences

“…Many non‐ Saccharomyces yeasts cannot complete alcoholic fermentation by themselves, and therefore are often used together with Saccharomyces yeasts for wine production (Jolly et al., 2014). In natural fermentations, wild yeasts and fungi from vineyard soil and grapevine are transferred to the fermentation tank and dominant the microbial community of the grape must at early stage of fermentation, followed by continuous increasing proportion of Saccharomyces strain throughout the process (Liu, Chen, et al., 2020; Liu, Legras, et al., 2020). For controlled fermentations, specific non‐ Saccharomyces yeasts are deliberately added to the grape must, either in a mixed culture with Saccharomyces yeast or inoculated sequentially with non‐ Saccharomyces yeasts first followed by Saccharomyces , which simulates the process of natural fermentation (Benito et al., 2011; Cañas et al., 2014; Escott et al., 2018; Medina et al., 2016).…”

“…In recent years, the raising concept of “microbial terroir” has drawn researchers’ attention back to the importance of indigenous yeasts, mainly due to the fact that the microbial consortia inhabiting in the viticulture ecosystem are regional and site‐specific, and therefore could influence the development of wild fermentation in a more consistent way than researchers’ originally thoughts (Bokulich et al., 2014; Liu, Chen, et al., 2020). In another word, in the microorganism community, especially non‐ Saccharomyces yeasts originated from the vineyard ecosystem, are unique to each site, and could be transferred to the fermentation tank and actively contribute to the complexity and distinction of the wine, therefore reflecting the “terroir” (Capozzi et al., 2015; Liu, Chen, et al., 2020; Liu, Legras, et al., 2020). With understanding the importance of wild yeasts, researchers have been exploring the diversity of wild microorganism on vineyards as a reservoir for new yeast selection (Petruzzi et al., 2017).…”

“…With understanding the importance of wild yeasts, researchers have been exploring the diversity of wild microorganism on vineyards as a reservoir for new yeast selection (Petruzzi et al., 2017). An important reason to isolate these typicity related yeast is that the microbial community structure at a specific wine region can be influenced by the climatic condition and may vary from vintage to vintage despite of the nonrandom pattern at the regional and subregional level (Bokulich et al., 2014; Liu, Legras, et al., 2020). This fluctuation in microbial community could further influence the outcome of wild fermentation.…”

“…In fact, researchers around the world have been isolating local wild yeasts and investigating the impacts of mixed culture fermentation (including sequential inoculation) on the chemical (especially phenolics) and sensory attributes of wine using specific non‐ Saccharomyces yeasts together with S. cerevisiae (Escott et al., 2018; Escribano‐Viana et al., 2019; Medina et al., 2016; Minnaar et al., 2018). This approach is a simulation of the wild yeast fermentation process, where a mixture of diverse microorganisms including many non‐ Saccharomyces yeasts initiate the alcoholic fermentation, followed by rapid increase of S. cerevisiae that dominate the rest of fermentation (Liu, Legras, et al., 2020). Despite this fact, most of the past fermentation studies only mixed one strain of non‐ Saccharomyces yeast with one strain of S. cerevisiae for each fermentation trial rather than mixing multiple non‐ Saccharomyces yeasts.…”