Molecular characterization and lipase profiling of the yeasts isolated from environments contaminated with petroleum.

In the present study, 120 yeast isolates from different sources (active sludge, soil, and wastewater samples obtained from petroleum refinery and soil contaminated by petroleum) were obtained. The yeast isolates were screened for lipase production and twelve of the isolates (D3, D17, D24, D27, D30, D38, D40, D42, D44, D46, D56, and D57) exhibited lipase activity. Molecular characterization of the yeasts showing the lipase production was performed with RFLP of ITS1-5.8S-ITS2 and 18S rRNA and sequence analysis of D1/D2 domain of 26S rRNA. The 26S rRNA sequencing revealed that four new strains, D38, D40, D44 and D57 identified as Rhodotorula slooffiae, Candida davisiana, Cryptococcus diffluens, and Cryptococcus uzbekistanensis, respectively, are lipase producing yeast species. This study is the first report showed lipase production by these species. The other lipase producing strains identified as Candida parapsilosis (D3), Rhodotorula muciloginosa (D17 and D42), Cryptococcus albidus (D24, D27, D30, and D56), and Wickerhamomyces anomalus (D46).

Yalçın HT ，Corbacı C ，Uçar FB 《-》

Taxonomic and phenotypic characterization of yeasts isolated from worldwide cold rock-associated habitats.

Yeast strains isolated from rock samples collected from worldwide cold regions were identified by sequence analysis of the D1/D2 domains of the 26S rDNA gene and the ITS region followed by molecular phylogeny. Over 77% of yeasts isolates were Basidiomycota. Cryptococcus (orders Filobasidiales and Tremellales) and Rhodotorula (order Cystobasidiales) were the most frequent genera. About 40% of yeast isolates belonged to undescribed species. Almost all isolates were psychrotolerant. Urease and esterase were the most widely extracellular enzymatic activity at 4 °C and 20 °C. None of the strains exhibited extracellular protease, DNAse, cellulase, chitinase, and laccase activity. The taxonomic and ecological significance of yeasts associated to worldwide cold rocky habitats is discussed.

Selbmann L ，Zucconi L ，Onofri S ，Cecchini C ，Isola D ，Turchetti B ，Buzzini P ... -  《Fungal Biology》

Isolation and molecular characterization of biosurfactant producing yeasts from the soil samples contaminated with petroleum derivatives.

In this study, 65 yeast strains were isolated from different environmental samples contaminated with various petroleum hydrocarbons such as activated sludges and soil samples from automobile workshops. The yeast isolates were tested for biosurfactant production using various screening methods such as parafilm M test, oil displacement assay, drop collapse assay, determination of surface tension reduction, and emulsification index. Nineteen of the isolates were found positive for biosurfactant production and their molecular characterizations were carried out by sequencing analysis of the ITS1-5.8S-ITS2 region and D1/D2 domain of 26S rDNA. The results indicated that these strains were from a wide range of yeast genera including Rhodotorula, Candida, Yarrowia, Geotrichum, Galactomyces, and Cystobasidium. The studies to determine the emulsification index revealed that the biosurfactants produced by Yarrowia lipolytica strains (TEMGS33, TEMOS12, and TEMOS14) and Apiotrichum loubieri strain (TEMOS16) were the most potent and capable of forming stable emulsions with emulsion index (E24 ) up to 68%. In addition, quantitative measurements of the surface tension reduction of the biosurfactants produced by these strains were carried out by Du Noüy ring method. Biosurfactants produced from Yarrowia lipolytica strain TEMGS33 and Apiotrichum loubieri strain TEMOS16 gave the best results reducing the surface tension to 34.7 ± 1.15 and 35.3 ± 0.55 mN m-1 , respectively. Based on these data, biosurfactants from Yarrawia lipolytica strains (TEMGS33, TEMOS12, and TEMOS14) and Apiotrichum loubieri strain (TEMOS16) showed promising results and might be implemented in numerous industrial fields such as bioremediation and food industry.

Yalçın HT ，Ergin-Tepebaşı G ，Uyar E 《-》

Use of PCR-restriction fragment length polymorphism analysis for identification of yeast species isolated from bovine intramammary infection.

This study reports a rapid PCR-based technique using a one-enzyme RFLP for discrimination of yeasts isolated from bovine clinical and subclinical mastitis milk samples. We analyzed a total of 1,486 milk samples collected over 1 yr in south Sardinia and northern Italy, and 142 yeast strains were preliminarily grouped based on their cultural morphology and physiological characteristics. Assimilation tests were conducted using the identification kit API ID 32C and APILAB Plus software (bioMérieux, Marcy l'Etoile, France). For PCR-RFLP analysis, the 18S-ITS1-5.8S ribosomal(r)DNA region was amplified and then digested with HaeIII, and dendrogram analysis of RFLP fragments was carried out. Furthermore, within each of the groups identified by the API or PCR-RFLP methods, the identification of isolates was confirmed by sequencing of the D1/D2 region using an ABI Prism 310 automatic sequencer (Applied Biosystems, Foster City, CA). The combined phenotypic and molecular approach enabled the identification of 17 yeast species belonging to the genera Candida (47.9%), Cryptococcus (21.1%), Trichosporon (19.7%), Geotrichum (7.1%), and Rhodotorula (4.2%). All Candida species were correctly identified by the API test and their identification confirmed by sequencing. All strains identified with the API system as Geotrichum candidum, Cryptococcus uniguttulatus, and Rhodotorula glutinis also produced characteristic restriction patterns and were confirmed as Galactomyces geotrichum (a teleomorph of G. candidum), Filobasidium uniguttulatum (teleomorph of Crypt. uniguttulatus), and R. glutinis, respectively, by D1/D2 rDNA sequencing. With regard to the genus Trichosporon, preliminary identification by API was problematic, whereas the RFLP technique used in this study gave characteristic restriction profiles for each species. Moreover, sequencing of the D1/D2 region allowed not only successful identification of Trichosporon gracile where API could not, but also correct identification of misidentified isolates. In conclusion, the 18S-ITS1-5.8S region appears to be useful in detecting genetic variability among yeast species, which is valuable for taxonomic purposes and for species identification. We have established an RFLP database for yeast species identified in milk samples using the software GelCompar II and the RFLP database constitutes an initial method for veterinary yeast identification.

Fadda ME ，Pisano MB ，Scaccabarozzi L ，Mossa V ，Deplano M ，Moroni P ，Liciardi M ，Cosentino S ... -  《-》

Molecular phylogeny of basidiomycetous yeasts in the Cryptococcus luteolus lineage (Tremellales) based on nuclear rRNA and mitochondrial cytochrome b gene sequence analyses: proposal of Derxomyces gen. nov. and Hannaella gen. nov., and description of eigh

Wang QM ，Bai FY 《FEMS YEAST RESEARCH》