Yeast diversity during the fermentation of Andean chicha: A comparison of high-throughput sequencing and culture-dependent approaches. (October 2017) - Mendoza, Lucía M.
Abstract: Diversity and dynamics of yeasts associated with the fermentation of Argentinian maize-based beverage chicha was investigated. Samples taken at different stages from two chicha productions were analyzed by culture-dependent and culture-independent methods. Five hundred and ninety six yeasts were isolated by classical microbiological methods and 16 species identified by RFLPs and sequencing of D1/D2 26S rRNA gene. Genetic typing of isolates from the dominant species, Saccharomyces cerevisiae, by PCR of delta elements revealed up to 42 different patterns. High-throughput sequencing (HTS) of D1/D2 26S rRNA gene amplicons from chicha samples detected more than one hundred yeast species and almost fifty filamentous fungi taxa. Analysis of the data revealed that yeasts dominated the fermentation, although, a significant percentage of filamentous fungi appeared in the first step of the process. Statistical analysis of results showed that very few taxa were represented by more than 1% of the reads per sample at any step of the process. S. cerevisiae represented more than 90% of the reads in the fermentative samples. Other yeast species dominated the pre-fermentative steps and abounded in fermented samples when S. cerevisiae was in percentages below 90%. Most yeasts species detected by pyrosequencing were not recovered by cultivation. In contrast, the cultivation-based methodology detected very few yeast taxa, and most of them corresponded with very few reads in the pyrosequencing analysis. Highlights: HTS of D1/D2 26S rDNA amplicons revealed large yeast diversity in chicha fermentation. Non- Saccharomyces yeasts species detected by pyrosequencing could not be isolated. Dominant Saccharomyces cerevisiae was isolated as well as detected by pyrosequencing. Non- Saccharomyces yeasts dominated pre-fermentative steps in chicha production. A rich genetic diversity of S. cerevisiae strains was observed in chicha fermentation.