Thermotolerant yeasts from fermentation of Coffea arabica L. cv. Catuaí from Panama and their effects on coffee quality

Abstract Background Microbial diversity during coffee fermentation has been suggested to be specific to each geographical region. However, more studies are required to understand yeast preference for a particular coffee variety, niche, their response to fermentation methods or to climate change. The aim of this study was to isolate and identify yeasts participating in fermentation of Coffea arabica L. cv. Catuaí from Boquete in the Republic of Panama using molecular data. We selectively targeted thermotolerant yeasts that may be further evaluated for their capacity to become starter cultures. Results The diversity of yeasts was surprisingly high: 32 OTUs out of 80 isolates. BLAST analyses of nuclear ribosomal internal transcribed spacers and 5.8S (i.e., ITS rDNA) sequences of all isolated strains, cultured during the fermentation process, showed they belong to five different clades corresponding to genera Clavispora, Nakaseomyces, Meyerozyma, Candida and Pichia. The major representative genera found at the beginning of the fermentation process were Clavispora and Meyerozyma. Pichia was cultured only after 8 hours of fermentation and persisted as the main isolated genus until the end of the process. Conclusions With this method, two strains belonging to Pichia and one to Clavispora were selected as starter cultures producing coffee that ranked over 81 points in the Specialty Coffee Associations scale. An unexpectedly high species diversity was found, suggesting that previous studies using lower isolation temperatures may have missed several thermotolerant or thermophilic taxa. Thus, a method used to specifically isolate thermotolerant microorganisms was successfully applied to target potentially useful strains to create starter cultures in a fast and efficient manner.