Ethanol productivity of cryophilic basidiomycetous yeast Mrakia spp. correlates with ethanol tolerance

Abstract

Twenty-seven strains of basidiomycetous yeast Mrakia spp. were collected from lake sediment and soil surrounding the lakes in the Skarvsnes area, East Antarctica. Based on sequence similarity of their ribosomal internal transcribed spacer regions and D1/D2 domains, the isolated strains were classified into three species; Mrakia blollopis (18 strains), M. gelida (7 strains), and M. robertii (2 strains). All of the strains produced ethanol from glucose at 10 °C. Six strains selected from the 27 isolates were then tested for ethanol fermentation and ethanol tolerance at 100 g/l glucose. Mrakia blollopis SK-4 and M. blollopis NRI-4 completely consumed the glucose within 13 d and 6 d of fermentation respectively, and demonstrated high ethanol yields and ethanol tolerance. In contrast, M. blollopis AGK-3 and M. blollopis TKG1-2 exhibited low ethanol yields and poor ethanol tolerance. These results indicate that ethanol yields of different Mrakia species may depend on ethanol tolerance in individual strains.