Yeast communities associated with artisanal mezcal fermentations from Agave salmiana

Abstract

The aims of this work were to characterize the fermentation process of mezcal from San Luis Potosi, México and identify the yeasts present in the fermentation using molecular culture-dependent methods (RFLP of the 5.8S-ITS and sequencing of the D1/D2 domain) and also by using a culture-independent method (DGGE). The alcoholic fermentations of two separate musts obtained from Agave salmiana were analyzed. Sugar, ethanol and major volatile compounds concentrations were higher in the first fermentation, which shows the importance of having a quality standard for raw materials, particularly in the concentration of fructans, in order to produce fermented Agave salmiana must with similar characteristics. One hundred ninety-two (192) different yeast colonies were identified, from those present on WL agar plates, by RFLP analysis of the ITS1-5.8S- ITS2 from the rRNA gene, with restriction endonucleases, HhaI, HaeIII and HinfI. The identified yeasts were: Saccharomyces cerevisiae, Kluyveromyces marxianus, Pichia kluyveri, Zygosaccharomyces bailii, Clavispora lusitaniae, Torulaspora delbrueckii, Candida ethanolica and Saccharomyces exiguus. These identifications were confirmed by sequencing the D1-D2 region of the 26S rRNA gene. With the PCR-DGGE method, bands corresponding to S. cerevisiae, K. marxianus and T. delbrueckii were clearly detected, confirming the results obtained with classic techniques.

Ploidy Variation in Kluyveromyces marxianus Separates Dairy and Non-dairy Isolates

“…This association with fermented dairy beverages, a consequence of its capacity to use the milk sugar lactose as a carbon source, has led to inclusion of K. marxianus on GRAS (FDA) and QPS (EU) lists of safe micro-organism for use in foods (Lane and Morrissey, 2010 ; Ricci et al, 2017 ). The yeast is also regularly isolated from non-dairy environments (e.g., decaying fruit) and is part of the natural flora involved in production of Agave -based alcoholic beverages such as tequila and mezcal (Lappe-Oliveras et al, 2008 ; Verdugo Valdez et al, 2011 ). In the latter case, the production of enzymes that degrade plant fructans to simpler sugars (inulinases) undoubtedly contributes to its growth in this environment (Arrizon et al, 2012 ).…”

Winemaking and Bioprocesses Strongly Shaped the Genetic Diversity of the Ubiquitous Yeast Torulaspora delbrueckii

“…T. delbrueckii is also naturally associated with several other human bioprocesses, ranging from food fermentations of silage, cocoa [29], [30], olive [31] or cucumber [32], [33], to distilled and traditional fermented beverage production including mezcal [34], colonche [35], tequila [36], cider [37], strawberry tree fruits juice [38], sugarcane juice [39], [40] and kefir [41]. T. delbrueckii is a frequent component of dairy products' microflora, either as desirable ferment for traditional cheeses [42] and fermented milk [43], or as spoilage yeast [44], [45].…”

Fermentative capabilities of native yeast strains grown on juices from different Agave species used for tequila and mezcal production

“…They were unable to isolate S. cerevisiae, probably because of the saponins contained on the juice. Conversely, Verdugo et al (2011) [27] isolated and identified S. cerevisiae strains during the spontaneous fermentation of A. salmiana juice, although they did not mention if these S. cerevisiae strains are able to ferment when grown on this agave juice. The results obtained in this work may be explained by the fact that both Agave species (A. salmiana and A. durangensis) display the highest saponin content ( Table 2).…”