A basidiomycetous yeast, Pseudozyma tsukubaensis, efficiently produces a novel glycolipid biosurfactant. The identification of a new diastereomer of mannosylerythritol lipid-B

Mannosylerythritol lipids (MELs) are glycolipid biosurfactants produced by the yeast strains of the genus Pseudozyma. These compounds show not only excellent surface-active properties but also versatile biochemical activities. In the course of MEL production by Pseudozyma tsukubaensis, we found an unusual MEL that had a different carbohydrate structure from that of conventional MELs. The carbohydrate structure was identified as 1-O-β-d-mannopyranosyl-d-erythritol, and the MEL was confirmed to be 1-O-β-(2′,3′-di-O-alka(e)noyl-6′-O-acetyl-d-mannopyranosyl)-d-erythritol. Interestingly, the configuration of the erythritol moiety in the present MEL was opposite to that of the known MEL-B, 4-O-β-(2′,3′-di-O-alka(e)noyl-6′-O-acetyl-d-mannopyranosyl)-d-erythritol, and to that of all MELs hitherto reported. The present MEL should thus provide different interfacial and biochemical properties compared to conventional MELs.