Wickerhamomyces psychrolipolyticus f.a., sp. nov., a novel yeast species producing two kinds of lipases with activity at different temperatures.

Two yeast strains isolated from soil collected in Hokkaido, Japan, were found to secrete two extracellular lipases that exhibited activities at both 25 and 4 °C. Both strains could utilize olive oil, rapeseed oil, lard and fish oil as sole carbon sources. The similarity of the D1/D2 domain of the large subunit ribosomal RNA (LSU rRNA) sequence of these yeast strains to that of other yeasts in the GenBank database was very low (<96 %). The phylogenetic trees based on the LSU rRNA sequences and translation elongation factor-1-α (tef1-α) sequences indicated that both strains represented a member of the Wickerhamomyces /Candida clade. Sexual reproduction was not observed. The name Wickerhamomyces psychrolipolyticus f.a., sp. nov is proposed for this newly described yeast species producing cold-active lipases. This novel species is distinguishable from the type strains of other related species, Wickerhamomyces alni, Candida ulmi and Candida quercuum due to their abilities to grow at 4 to 30 °C, to produce lipase that is active also at 4 °C and to assimilate soluble starch.

Genome-Wide Editing Provides Insights into Role of Unsaturated fatty Acids in Low Temperature Growth of the Psychrotrophic Yeast Metschnikowia bicuspidata var. australis W7-5.

In order to know the function of C18:2 and C18:3 fatty acids in the cold growth of the psychrotrophic yeast M. bicuspidata var. australis W7-5, the mutant 1 without C18:2 fatty acid and the mutant 2 without C18:3 fatty acids were obtained. Only the trace amount of C18:2 fatty acid in the mutant 1 occurred while no C18:3 fatty acid in the mutant 2 was detected. The growth rate of only the mutant 1 cultured at 5 â„ƒ and 25 â„ƒ was significantly reduced compared with that of the wild-type strain W7-5. But there was no difference between the growth of the mutant 2 and that of the W7-5 strain. These meant that only C18:2 synthesized by the psychrotrophic yeast played an important role in cell growth at low temperature (5 °C) and high temperature (25 °C). Meanwhile, cell wall in the mutant 1 without C18:2 fatty acid gown at 5 and 25 °C was also negatively affected, leading to the reduced cell growth rate of the mutant 1 grown at 5 and 25 °C.