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 《-》

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 《-》

Characterization of a novel biosurfactant produced by Staphylococcus sp. strain 1E with potential application on hydrocarbon bioremediation.

A biosurfactant-producing bacterium (Staphylococcus sp. strain 1E) was isolated from an Algerian crude oil contaminated soil. Biosurfactant production was tested with different carbon sources using the surface tension measurement and the oil displacement test. Olive oil produced the highest reduction in surface tension (25.9 dynes cm(-1)). Crude oil presented the best substrate for 1E biosurfactant emulsification activity. The biosurfactant produced by strain 1E reduced the growth medium surface tension below 30 dynes cm(-1). This reduction was also obtained in cell-free filtrates. Biosurfactant produced by strain 1E showed stability in a wide range of pH (from 2 to 12), temperature (from 4 to 55 °C) and salinity (from 0 to 300 g l(-1)) variations. The biosurfactant produced by strain 1E belonged to lipopeptide group and also constituted an antibacterial activity againt the pathogenic bacteria such as Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Bacillus subtilis. Phenanthrene solubility in water was enhanced by biosurfactant addition. Our results suggest that the 1E biosurfactant has interesting properties for its application in bioremediation of hydrocarbons contaminated sites.

Eddouaouda K ，Mnif S ，Badis A ，Younes SB ，Cherif S ，Ferhat S ，Mhiri N ，Chamkha M ，Sayadi S ... -  《-》

Diversity of biosurfactant producing microorganisms isolated from soils contaminated with diesel oil.

Menezes Bento F ，de Oliveira Camargo FA ，Okeke BC ，Frankenberger WT Jr ... -  《MICROBIOLOGICAL RESEARCH》

Biosurfactant production from newly isolated Rhodotorula sp.YBR and its great potential in enhanced removal of hydrocarbons from contaminated soils.

Derguine-Mecheri L ，Kebbouche-Gana S ，Djenane D 《-》