Thermo-and salt-tolerant Saccharomyces cerevisiae strains isolated from fermenting coconut toddy from Sri Lanka
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‘Toddy’ is an alcoholic beverage obtained by the natural fermentation of phloem sap. We isolated 27 yeast strains from coconut toddy in Sri Lanka. Sequences of the 26S rDNA gene D1/D2 region from 18 strains showed 100% identity to Saccharomyces cerevisiae, while eight strains showed 99% identity to Pichia manshurica and a single isolate showed 99% identity to Saccharomycodes ludwigii. Regarding salt tolerance, all isolated strains of S. cerevisiae were found to grow in the presence of 10.0% (w/v) NaCl in yeast extract-peptone-dextrose (YPD), one of the isolates (SLY-10) grew even with 13.0% (w/v) NaCl. All the isolates grew well at 40 °C, and the 18 S. cerevisiae strains showed significant growth even at 42 °C. All the 18 S. cerevisiae strains still showed growth better than reference strains did in a medium with 7.5% (w/v) NaCl at 40 °C. All S. cerevisiae isolates produced relatively high alcohol concentrations than reference strains did when growing on batch-fermented media with 100 g·L−1glucose in at 40 °C. The five strains (SLY-3, SLY-4, SLY-8, SLY-9 and SLY-10) produced significant amounts of alcohol even at 45 °C: alcohol productivity over 24 h at 40 °C and 45 °C was similar in two different glucose concentrations, and the amount of produced alcohol was higher with 160 g·L−1 glucose than with 100 g·L−1glucose, significantly at 45 °C.