A total of 71 isolates were collected from lake sediment and soil surrounding lakes in the Skarvsnes area, Antarctica. Based on ITS region sequence similarity, these isolates were classified to 10 genera. Twenty-three isolates were categorized as ascomycetous fungi from five genera (Embellisia, Phoma, Geomyces, Tetracladium or Thelebolus) and 48 isolates were categorized as basidiomycetous fungi in five genera (Mrakia, Cryptococcus, Dioszegia, Rhodotorula or Leucosporidium). Thirty-five percent of culturable fungi were of the genus Mrakia. Eighteen isolates from eight genera were selected and tested for both antifreeze activity and capacity for growth under temperatures ranging from -1 to 25 °C. Rhodotorula sp. NHT-2 possessed a high degree of sequence homology with R. gracialis, while Leucosporidium sp. BSS-1 possessed a high degree of sequence homology with Leu. antarcticum (Glaciozyma antarctica), and these two isolates demonstrated antifreeze activity. All isolates examined were capable of growth at -1 °C. Mrakia spp., while capable of growth at -1 °C, did not demonstrate any antifreeze activity and exhibited only limited secretion of extracellular polysaccharides. Species of the genus Mrakia possessed high amounts of unsaturated fatty acids, suggesting that members of this genus have adapted to cold environments by increasing their membrane fluidity.
The yeast Kluyveromyces marxianus is considered as a potential alternative to Saccharomyces cerevisiae in producing ethanol as a biofuel. In this study, we investigated the ethanol fermentation properties of novel K. marxianus strain DMB1, isolated from bagasse hydrolysates. This strain utilized sorbitol as well as various pentoses and hexoses as single carbon sources under aerobic conditions and produced ethanol from glucose in hydrolysates of the Japanese cedar at 42 °C. Reference strains K. marxianus NBRC1777 and S. cerevisiae BY4743 did not assimilate sorbitol or ferment lignocellulosic hydrolysates to ethanol at this temperature. Thus strain DMB1 appears to be optimal for producing bioethanol at high temperatures, and might provide a valuable means of increasing the efficiency of ethanol fermentation.
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