AimsThe aim of this study was to isolate a novel yeast strain, evaluate biosurfactant production by the strain and characterize the major product. Methods and ResultsThe strain SAM20, isolated from grass, identified as Sporisorium sp. aff. sorghi based on phylogenetic analyses. The strain produced approximately 32gl(-1) glycolipid biosurfactants from 40gl(-1) soybean oil after 7days at 28 degrees C. The glycolipids showed a unique pattern of mannosylerythritol lipids (MELs) on thin layer chromatography plate compared to those hitherto reported. Structural characterization of the major product, called GL-A, revealed that it was mainly tri-acetylated mono-acylated MELs (MEL-A2) with C14:0, C16:0, C12:0 or C14:1 as the hydrophobic chain. The critical micelle concentration (CMC), the surface tension at CMC and hydrophilic-lipophilic balance value for GL-A were estimated to be 20mgl(-1), 300mNm(-1) and 87, respectively. ConclusionsA MEL-A2 with novel composition and surface activities was efficiently produced from a novel MEL producer. This is the first report on production of MEL-A2 as the major product and from soybean oil. The biosurfactant has potential application as a wetting agent and oil-in-water emulsifier. Significance and Impact of the StudyDiscovery of novel structures and novel strains is valuable for further commercial development and application of MELs. Sporisorium sp. aff. sorghi SAM20 can be considered as a potential candidate for commercial production of biosurfactants.