Natural wine today represents one of the most fascinating and authentic frontiers in winemaking, a return to origins that values spontaneous processes and the biodiversity of the territories. In this context, wild yeasts play a fundamental role, transforming grape must into a complex beverage rich in nuances. But what connects these microorganisms to the kingdom of fungi? And how do they interact with the vineyard ecosystem? This article explores in depth the connections between mycology and winemaking, analyzing the role of native yeasts, spontaneous fermentation techniques and the impact of agricultural practices on fungal biodiversity. Through scientific data, case studies and technical insights, we will discover how fungi and yeasts contribute to creating unique wines and authentic expressions of terroir.
Oenological mycology is a rapidly evolving discipline that combines traditional knowledge with innovative scientific research. Yeasts, belonging to the kingdom of fungi, are the true architects of the transformation of must into wine, and their genetic diversity profoundly influences the organoleptic characteristics of the final product. In an era where standardization threatens the identity of wines, the rediscovery of indigenous yeasts represents not only a qualitative choice but also a stand in favor of biodiversity and sustainability. On this journey through the world of wild yeasts, we will examine the most important species for winemaking, their interactions with the environment, techniques to favor controlled spontaneous fermentations and the resulting sensory benefits. We will discover how natural winemakers are rediscovering ancient practices and how scientific research is providing new tools to understand and manage these fascinating microorganisms. Yeasts represent a heterogeneous group of unicellular fungi, predominantly ascomycetes and basidiomycetes, which reproduce by budding or fission. Although often simply associated with alcoholic fermentation, yeasts constitute a complex and diverse universe, with over 1500 described species. Their classification has evolved significantly in recent decades, thanks to the use of molecular techniques that have redefined phylogenetic relationships within the kingdom of fungi. Yeasts are eukaryotic organisms, generally between 3 and 40 micrometers in size, which present different modes of reproduction. Most species are capable of reproducing both asexually, through budding or binary fission, and sexually, forming asci or basidia. The cell wall of yeasts, composed mainly of glucans, mannans and chitin, represents a distinctive characteristic that links them to other fungi. This structure not only provides mechanical protection but also influences interactions with the environment and resistance to osmotic and thermal stresses. From a metabolic point of view, yeasts show remarkable versatility, being able to use different carbon sources through aerobic and anaerobic metabolic pathways. The ability to ferment sugars in the absence of oxygen, producing ethanol and carbon dioxide, represents the most exploited characteristic in oenology. However, many species also possess complete oxidative metabolisms, allowing them to survive in aerobic environments using a wide range of organic compounds. The landscape of yeasts involved in winemaking processes is extremely varied, with species belonging to different genera and families. The genus Saccharomyces, and particularly Saccharomyces cerevisiae, is historically the most studied and used in winemaking, but numerous other species contribute to the wine's sensory complexity. Among these, the genera Hanseniaspora, Candida, Pichia, Metschnikowia and Torulaspora play important roles in the initial stages of fermentation and in the formation of the aromatic profile. Understanding this diversity is fundamental to correctly approach natural winemaking, as each species contributes specifically to the development of the wine's sensory profile. Indigenous yeast communities represent a unique genetic heritage, closely linked to the territory and agricultural practices, whose conservation is essential to maintain oenological diversity. To learn more about the classification and characteristics of yeasts, we recommend consulting the Italian Mycology portal, which offers detailed fact sheets on the different fungal species. The vineyard represents a complex ecosystem, where yeasts interact with plants, soil, insects and microorganisms in a delicate balance. The distribution and diversity of yeast populations are influenced by numerous environmental and agronomic factors, which determine the specific microbiological imprint of each territory. Understanding these ecological dynamics is essential for those practicing natural winemaking, as it allows them to maximize the microbiological potential of their vineyard. Yeasts are distributed unevenly within the vineyard, with specific concentrations and compositions that vary depending on the microhabitat considered. Research has shown that the yeast population present on grape skins differs significantly from that of the soil, leaves, or winery equipment. This spatial distribution is influenced by factors such as sun exposure, relative humidity, nutrient availability and interactions with other microorganisms. A study conducted in various Italian vineyards highlighted that yeast biodiversity is highest in the soil, where up to 20-30 different species can be identified, while on grape skins the dominant species are generally reduced to 5-10. This reduction in diversity is compensated by ecological specialization, with strains particularly adapted to resist the specific conditions of the berry surface, such as high sugar concentration, acidity and exposure to UV rays. Numerous agronomic and environmental factors influence the composition and dynamics of yeast populations in the vineyard. Among these, soil management practices, the use of phytosanitary products, grape variety, climate and the presence of insect vectors play determining roles. Organic and biodynamic viticulture, characterized by lower environmental impact and greater attention to biodiversity, tend to favor more diverse and resilient yeast communities. Understanding these factors allows winegrowers to adopt management strategies that favor the presence of desirable yeasts and limit the development of harmful species. Conserving yeast biodiversity represents a long-term investment for wine quality and identity, especially in a context of climate change that could alter existing microbiological balances. For further insights into yeast ecology in viticulture, we suggest consulting the Wine Organic website, which dedicates ample space to sustainable practices in the winery. The choice between spontaneous fermentation and inoculation with selected yeasts represents one of the most significant decisions in the winemaking process, reflecting not only different technical approaches but genuine production philosophies. While the use of selected strains offers greater control and predictability, spontaneous fermentation enhances the microbiological specificity of the territory, producing more complex wines linked to the terroir. This paragraph analyzes in detail the advantages, limits and implications of both approaches. Spontaneous, or natural, fermentation occurs thanks to the action of indigenous yeasts naturally present on grape skins and in the winery environment. This process involves an ecological succession of different yeast species, each of which contributes specifically to the development of the wine's sensory profile. The initial stages are generally dominated by apiculate yeasts of the genera Hanseniaspora and Kloeckera, which produce a range of esters and aromatic compounds. Subsequently, with the increase in alcohol concentration, these species give way to Saccharomyces cerevisiae, which completes the fermentation of residual sugars. The main advantages of spontaneous fermentation include: greater aromatic complexity, due to the multiplicity of species and strains involved; better integration with the terroir, as indigenous yeasts are a specific expression of the vineyard-winery ecosystem; greater aromatic persistence and better aging capacity, thanks to the production of more diverse secondary compounds. However, this approach also presents significant rsks, including slow or stuck fermentations, development of undesirable characteristics and lower predictability of the final result. The use of selected yeasts, isolated and multiplied in the laboratory, represents the dominant approach in conventional viticulture. These strains are chosen for specific characteristics such as high alcohol tolerance, production of desired aromas, resistance to high temperatures or sulfur dioxide pressures. Controlled inoculation allows for a rapid start of fermentation, reducing the risks of undesirable microbial developments and ensuring a complete and predictable transformation of sugars. In recent years, an intermediate approach has been spreading, combining elements of both philosophies. Some producers use native starters, i.e., yeasts isolated from their own vineyard and multiplied in the winery, thus achieving a compromise between authenticity and control. Others practice sequential inoculations, starting fermentation with selected yeasts and letting indigenous yeasts complete the process. The choice of fermentative approach depends on the specific conditions, quality objectives and production philosophy of each winery. The fermentation of grape must involves a complex community of yeasts, traditionally divided into two broad categories: Saccharomyces and non-Saccharomyces. While the former, and particularly Saccharomyces cerevisiae, are responsible for most of the transformation of sugars into alcohol, the latter contribute decisively to the formation of the aromatic profile and the complexity of the wine. Understanding the interactions between these groups is fundamental to correctly managing spontaneous fermentations and obtaining quality wines. Saccharomyces cerevisiae is without doubt the most important yeast in oenology, thanks to its high alcohol tolerance (up to 15-16%), its ability to efficiently ferment sugars and its resistance to stress conditions such as low pH and the presence of sulfites. This yeast is generally dominant in the final stages of fermentation, when the alcohol concentration becomes incompatible with the survival of more sensitive species. In addition to ethanol production, S. cerevisiae synthesizes numerous compounds that influence the wine's sensory profile, including glycerol (which contributes to softness), organic acids and sulfur compounds. The intraspecific diversity of S. cerevisiae is remarkable, with hundreds of different strains characterized by distinctive metabolic properties. Indigenous strains of S. cerevisiae represent a unique genetic heritage, adapted to the specific conditions of each territory and able to best express the potential of each grape variety. The natural selection of these strains over the centuries has created specialized populations that contribute to the identity of traditional wines. Non-Saccharomyces yeasts, once considered simple contaminants or spoilage agents, are now recognized as essential components for the aromatic complexity of wines. These yeasts, which include genera such as Hanseniaspora, Candida, Pichia, Metschnikowia and Torulaspora, are generally active in the early stages of fermentation, when the alcohol concentration is still low. Their metabolic contribution includes the production of hydrolytic enzymes that release varietal aromas, the synthesis of fruity esters and the modification of aromatic precursors. Interactions between Saccharomyces and non-Saccharomyces are complex and can be both competitive and synergistic. Some non-Saccharomyces species produce compounds that inhibit S. cerevisiae, while others create favorable conditions for its development. Managing this ecological succession represents one of the most fascinating challenges of natural winemaking, requiring careful observation and deep knowledge of the behavior of different microorganisms. Wine: the hidden world of yeasts in vineyards
Yeasts in the kingdom of fungi: classification and characteristics
Biological characteristics of yeasts
Taxonomic diversity of oenological yeasts
Genus Main characteristics Role in fermentation Alcohol tolerance Saccharomyces Oval cells, asexual reproduction by budding Main fermentation Up to 15-16% Hanseniaspora Apiculate cells, predominantly oxidative metabolism Initial phase Up to 4-6% Candida Pseudomycelium form, versatile metabolism Initial and intermediate phase Up to 8-10% Pichia Surface film form, oxidative metabolism Initial phase, possible spoilage Up to 10-12% Metschnikowia Elongated cells, significant enzymatic activity Initial phase, aroma production Up to 6-8% Yeast ecology in the vineyard: a complex ecosystem
Spatial distribution of yeasts in the vineyard
Factors influencing the yeast community
Agronomic practice Effect on biodiversity Impact on fermentation Recommendations Organic Fertilization Increase in species-specific diversity More complex and gradual fermentations Use mature compost and well-seasoned manure Controlled Cover Cropping Greater species richness in soil Larger available genetic pool Maintain floristic diversity between rows Copper Treatments Selective reduction of sensitive species Possible simplification of aromatic profile Limit treatments close to harvest Integrated Pest Management Balance between diversity and pathogen control More stable and predictable communities Prefer mechanical and biological methods Spontaneous fermentation vs selected inoculum: pros and cons
Spontaneous Ffermentation: complexity and authenticity
Inoculation with selected yeasts: control and safety
Parameter Spontaneous fermentation Selected inoculum Aromatic Complexity Very High Medium-Low Expression of Terroir Maximum Limited Predictability Low Very High Risk of Alterations Medium Low Fermentation Time Variable (10-30 days) Controlled (5-10 days) Production Cost Low (no yeast purchase) Medium (cost of yeasts) Saccharomyces cerevisiae and non-saccharomyces yeasts: a dynamic balance
The role of saccharomyces cerevisiae in winemaking
Contribution of non-saccharomyces yeasts to wine complexity
Species Aromatic compounds produced Sensory effect Phase of activity Hanseniaspora uvarum 2-Phenylethyl acetate, isoamyl acetate Floral, fruity aroma First 2-4 days Metschnikowia pulcherrima Monoterpenes, varietal thiols Citrusy, exotic fruit aroma First 3-5 days Torulaspora delbrueckii Ethyl esters, fatty acids Complexity, persistence First 5-7 days Lachancea thermotolerans Lactic acid Softness, acidity First half of fermentation Pichia kluyveri Thiols, fruity esters Aromatic intensity First 3-6 days