Search for Natural Glycerol-Producing Yeast Strains

Screening of glycerol-producing yeasts resistant to high osmotic pressure of substrates has been carried out among collection strains and strains isolated from natural sources associated with bee habitat. In total, more than 170 strains of osmotolerant yeasts were investigated which belong to 9 genera and the following13 species: Candida apicola, C. magnolia, Debaryomyces hansenii, D. marama, D. polymorphus, Hansenula ciferri, Kluyveromyces lactis, K. marxianus, Pichia farinose, Saccharomyces cerevisiae, Starmerella bombi, Schizosaccharomyces pombe, and Zhygosaccharomyces rouxii. The Kluyveromyces lactis VKPM Y-4429 strain producing 77.4 g/L of glycerol for 24 h of cultivation on media with a high glucose (300 g/L) and NaCl (5-6%) content was selected. These conditions cause osmotic shock, and as a consequence, a higher glucose conversion to glycerol. glycerol biosynthesis, fermentation, osmotolerant yeast, screening The work was supported by the State Assignment № AAAA-A20-120093090016-9 and the work was carried out using the Unique Scientific Facility of the "All-Russian Collection of Industrial Microorganisms" National Bio-Resource Center, NRC «Kurchatov Institute»---GOSNIIGENETIKA (NBC VKPM).

Starmerella neotropicalis f. a., sp. nov., a yeast species found in bees and pollen

A novel yeast species was found repeatedly and in high cell densities in underground-nesting stingless bees of the species Melipona quinquefasciata and their provisions in northern Minas Gerais (Brazil). One additional strain was isolated from bee-collected pollen in Cuba. Phylogenetic analyses based on rRNA gene sequences (D1/D2 large subunit gene and internal transcribed spacer) indicated that the novel species belongs to the Starmerella clade and is most closely related to Candida (iter. nom. Starmerella) apicola. Growth reactions on carbon and nitrogen sources were typical of those observed in related species of the Starmerella clade. PCR-fingerprinting with mini- and microsatellite specific primers allowed the distinction of the novel species from Candida apicola, Candida bombi and a yet undescribed species represented by strain CBS 4353. On the basis of phylogenetic relationships, the novel species is assigned to the genus Starmerella despite the failure to observe sexual reproduction after extensive mating tests. We propose the name Starmerella neotropicalis f. a., sp. nov. (Mycobank MB 804285) and designate UFMG PST 09T ( = MUCL 53320T = CBS 12811T) as the type strain.

Identification and Partial Characterization of Extracellular Aspartic Protease Genes from Metschnikowia pulcherrima IWBT Y1123 and Candida apicola IWBT Y1384

ABSTRACTThe extracellular acid proteases of non-Saccharomyceswine yeasts may fulfill a number of roles in winemaking, which include increasing the available nitrogen sources for the growth of fermentative microbes, affecting the aroma profile of the wine, and potentially reducing protein haze formation. These proteases, however, remain poorly characterized, especially at genetic level. In this study, two extracellular aspartic protease-encoding genes were identified and sequenced, from two yeast species of enological origin: one gene fromMetschnikowia pulcherrimaIWBT Y1123, namedMpAPr1, and the other gene fromCandida apicolaIWBT Y1384, namedCaAPr1.In silicoanalysis of these two genes revealed a number of features peculiar to aspartic protease genes, and both the MpAPr1 and CaAPr1 putative proteins showed homology to proteases of yeast genera. Heterologous expression ofMpAPr1inSaccharomyces cerevisiaeYHUM272 confirmed that it encodes an aspartic protease. MpAPr1 production, which was shown to be constitutive, and secretion were confirmed in the presence of bovine serum albumin (BSA), casein, and grape juice proteins. TheMpAPr1gene was found to be present in 12 otherM. pulcherrimastrains; however, plate assays revealed that the intensity of protease activity was strain dependent and unrelated to the gene sequence.