3.1 Isolation of ethanol-tolerant yeast species from Atacama Desert flora
To identify ethanol-tolerant yeast strains from the Atacama Desert, we collected 22 samples from various tissues of native trees, including bark, bark-exuded gum, pods, and flowers. The tree species sampled included Neltuma chilensis (Algarrobo), Geoffroea decorticans (Chañar) and Strombocarpa tamarugo (Tamarugo). After subjecting these samples to culture enrichment in rich media containing 4% ethanol, a total of 91 ethanol-tolerant yeast colonies were obtained (Table S1 ). Among these colonies, 60 were isolated fromN. chilensis , 10 from S. tamarugo , and 21 from G. decorticans .
To identify ethanol-tolerant yeasts, we amplified the ITS region and sequenced at least one colony per sample according to the size of the ITS region obtained. Based on these sequencing results, we identified 36 isolates as belonging to the basidiomycetous phylum, specifically the genera Kwoniella , Rhodotorula, and Naganishia.Additionally, we identified 55 isolates corresponding to ascomycetous species, belonging to the genera Zalaria, Starmerella , andNakazawaea .
To identify fermenting yeast, we conducted the Durham tube fermentation test using glucose as the carbon source. Through this test, we discovered thirty-nine isolates belonging to the generaNakazawaea . and Starmerella that exhibited the ability to ferment glucose. Notably, all of these isolates were obtained from samples of N.chilensis . This plant is a leguminous tree known for its high levels of polysaccharides (Astudillo et al. , 2000). It is also worth mentioning that the ’Aloja’ beverage is produced from the mashed pods of Neltuma species, suggesting a potential association between ethanol-tolerant yeasts and the spontaneous fermentation processes associated with this tree species. Among the isolates, the majority were identified as representatives of the genusNakazawaea (35 isolates). However, the ITS region of these isolates differed by 16 to 25% in terms of sequence identity from theNakazawaea species currently described (Figure S1 ). Hence, in this study, we focus on the description of a new fermenting ascomycetous yeast species, which we have named Nakazawaea atacamensis sp. nov.