Isolated Antarctic soil yeasts with fermentative capacity with potential use in the wine industry

Abstract

The wine industry is currently on the search for new aromas and less browning in their products. In the improvement process of wine, lower fermentation temperatures have been considered, however, the yeasts in the market cannot tolerate such temperatures. Therefore, an interesting place to find new yeasts with criotolerance is the Antarctic Continent.Our methodology to accomplish our objectives started with the isolation of yeast from soil using YM agar (yeast extract, malt extract, peptone, 1% glucose, and agar) with antibiotics. Then the isolates were submitted to a fermentation assay using a colorimetric indicator of pH variation. The samples positive for fermentative activity were then analyzed to determine tolerance to glucose:fructose 1:1, with the following concentration; 5,10,15,20, and 25%. The isolates were analyzed by their capacity to grow at different alcohol concentrations (3,6,9%).Then fingerprinting analysis was performed to select unique yeasts. Then ITS region was amplified and sequenced to identify the isolates.We were able to isolate 125 yeasts. Of which 25 had fermentative activity at 10ºC. These yeasts were used to analyze glucose tolerance and alcohol tolerance. All samples grew at 20% sugar content, and all samples grew at 6% alcohol content. Some of the isolates were capable of growing at the most extreme conditions, with 25% sugar content and 9% ethanol.After a fingerprinting assay, we reduced the candidates to 9 isolates. Then we determined the optimal growth temperature where we observed that our isolates have a longer latency period regarding S. cerevisiae, the Antarctic isolates grew better at 10 and 15ºC. Later on, we extracted DNA, performed a PCR for the ITS region, and sequenced the ITS regions to identify the isolates from Antarctica. Finally, the ITS sequenced regions were used to create a phylogenetic tree.The fermentative yeasts with high alcohol tolerance and fermentation at high concentrations of sugar will be used for micro-fermentation of synthetic must to determine their potential use in the production of Chilean wine