## 1 Introduction  
Beer is the most popular and widespread alcoholic drink in the world, offering a wide variety of styles and flavors around the globe [1]. The production of this beverage is determined by well-defined processes, such as malting, grinding and macroating the grains, cooking the word, and finally fermenting [2]. The final fermented product contains unique organoleptic properties, as a result of a delicate balance between aromas and flavors provided by the main ingredients used during the process: malt, water, hops, and yeast [3, 4]. Industrial beer production is dominated by yeasts belonging to the _Saccharomyces_ genus, mainly _Saccharomyces cerevisiae_ responsible for ale beer fermentation, while _S. pastorianus_ (a hybrid between _S. cerevisiae_\(\times\)_S. eubayanus_) is used for lager beers. Unlike ales, which are fermented by _S. cerevisiae_ in a range of 16-25 \({}^{\circ}\)C, lagers are fermented by _S. pastorianus_ at lower temperatures (8-15 \({}^{\circ}\)C), mostly because of the cryotolerant contribution of _S. eubayanus_ to the lager hybrid [5]. Lager beer represents more than 90% of the beer produced worldwide and is the most popular style consumed [6]. During fermentation, yeast cells produce a wide range of secondary metabolites, including volatile compounds (VCs) responsible for the complex flavors and aromas found in beer. VCs are molecules with low molecular weight and rapid dispersion in the environment and determine the different organoleptic qualities of beer [7, 8]. Some of the VCs found in beer are synthesized by yeast cells through several metabolic pathways, emphasizing that a significant contribution to the organoleptic properties of beer is provided by the particular strain used for fermentation [2]. Hence, the strains' genotype, together with environmental factors during fermentation, determines to a large extent the presence of these compounds in the final product [9]. For example, _S. pastorianus_ (employed in the production of _Piliser_-style _lager_) [10, 11] produces at low temperatures a subtle organoleptic profile mainly characterized by the presence of ester compounds such as ethyl acetate, ethyl lexanoate, and isoamyl acetate. On the other hand, _S. cerevisiae_ (employed to produce ale _craft_ beer fermented at high temperatures compared to lager) [10, 11] produces a wider range of VCs like \(\beta\)-myrceene, ethyl octanoate, \(\beta\)-linalool, ethyl decanoate, octanoic acid, decanoic acid, ethyl acetate, and ethyl propionate, among others, providing a more complex organoleptic profile in beer [11, 12]. The environmental stresses faced during the fermentation process, such as the presence of spoilage microorganisms, the fermentation temperature, nitrogen availability, and carbon sources in the word, also impact the VC profile of the beer [2, 7]. Therefore, depending on these variables, yeast cells produce different concentrations and types of VCs, allowing them to regulate their metabolism in terms of nitrogen uptake, membrane fluidity, and biomass generation [1, 6]. The most relevant VCs produced by yeast are esters, phenols, and alcohols derived from the Ehrlich route [2, 10]. However, most of the strains used in beer fermentation produce very similar and smooth organoleptic profiles, as found in many lager beers. While ale beers are marked by a broad array of esters and higher alcohols [1], lagers are generally characterized by a limited set of flavors and aromas [13]. For example, two commercial lager strains (Frisinga-TUM 3470 and Securitas-TUM 193) produced fewer esters and higher alcohols compared to a set of ale strains [14]. Interestingly, this set of ale strains showed different VC production profiles, demonstrating a pervasive intra-specific phenotypic variability among ale strains and a considerable impact on the final fermented product [14]. The lack of a wide range of VCs in lager styles is mostly explained by the low genetic diversity among _S. pastorianus_ strains, strongly limiting the variety of lager styles.