Impact of environmental conditions and process modifications on microbial diversity, fermentation efficiency and chemical profile during the fermentation of Mezcal in Oaxaca

- Microbial diversity of Mezcal fermentations has been determined.
- Production of volatile compounds has been monitored.
- Non-Saccharomyces yeasts coexist during fermentation along with S. cerevisiae.
- Preparation practices impact on microbiota composition and fermentation efficiency.

Mezcal, a distilled alcoholic beverage derived from cooked agave plants, is manufactured traditionally on a small scale where raw materials and production practices differ noticeably between production regions, localities and even factories resulting in a set of highly distinctive products. The present study aimed to draw a comprehensive picture of the mezcal production in Oaxaca State, relating the microbial consortia with the chemical compounds detected during mezcal fermentation, and to elucidate the impact of process modifications made in order to improve fermentation performance. In two mezcal distilleries, fermentation processes were monitored in two consecutive years. Isolated yeasts (553) and bacteria (527) were identified combining traditional and molecular techniques, detecting up to 21 different yeast species and 27 different bacterial species during a single process. Fermentation kinetics and volatile compound generation varied strongly between the studied processes. A highly diverse microbiota associated to these traditional alcoholic fermentations was detected wherein several yeast species and numerous bacterial groups built up the microbial consortia. Modifications introduced between two production seasons showed a clear impact on microbial diversity. The employment of wild inoculums increased alcoholic fermentation efficiency, nevertheless, prominent changes in the volatile compound profile should be taken into account.