Spontaneous fermentations contribute to the identity of ancestral mezcal, although duration and yield may vary. This study selected an indigenous yeast and evaluated it as a starter candidate. Four native isolates (Torulaspora delbrueckii A1GM and A6GM, Kluyveromyces marxianus A2GM, and Saccharomyces cerevisiae A5GM) and a spontaneous control were compared in Agave cupreata microfermentations. Selection considered distillate alcohol content and preliminary ethanol-tolerance assays. A5GM was subsequently evaluated in three production batches containing A. angustifolia + A. karwinskii, A. angustifolia, or A. cupreata + A. angustifolia, with three independent vats per treatment. Fermentation profiles, distillate composition, yield, and sensory acceptance were assessed. A5GM produced the highest microfermentation distillate alcohol content (43.91 ± 0.89% Alc. Vol.) and grew at 16% ethanol (v/v). In the first two production batches, inoculated vats showed higher volumes standardized to 45% Alc. Vol. and lower calculated agave requirements than the controls; these were batch-specific observations under the operating conditions studied. Sensory evaluation used pooled vat-derived distillate composites, and the A5GM composites received the highest mean hedonic scores. Because strain-level establishment and persistence of A5GM were not confirmed, the observed outcomes cannot be attributed exclusively to this strain. Sensory interpretation is limited by fixed presentation order. Further independent batches, standardized management, and strain-level monitoring are needed to assess reproducibility.

In Mexico, spirits reflect the country's cultural diversity and traditions, which vary according to region, season, and local customs. These beverages are not only a fundamental part of Mexican identity, but in recent years they have also gained popularity worldwide. They include distilled spirits, fermented beverages, liqueurs, and non-alcoholic beverages, which have stood out for their quality and authenticity. These products have consolidated their position as an essential part of Mexico's cultural wealth, becoming increasingly valued both nationally and internationally. However, despite the age of many of these beverages, there has been a lack of up-to-date information on their current status. Therefore, the present study aims to investigate Mexican spirits in order to identify the regions of production, the manufacturing processes, and the cultural relationship they maintain with each of these regions.