A basidiomycetous yeast, Pseudozyma crassa, produces novel diastereomers of conventional mannosylerythritol lipids as glycolipid biosurfactants

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 actions. During a survey of new MEL producers, we found that a basidiomycetous yeast, Pseudozyma crassa, extracellularly produces three glycolipids. When glucose and oleic acid were used as the carbon source, the total amount of glycolipids reached approximately 4.6 g/L in the culture medium. The structures of these glycolipids were similar to those of well-known MEL-A, -B, and -C, respectively. Very interestingly, in all the present glycolipids, the configuration of the erythritol moiety was entirely opposite to that of conventional MELs. The present glycolipids were identified to have the carbohydrate structure of 4-O-β-d-mannopyranosyl-(2R,3S)-erythritol, stereochemically different from 4-O-β-d-mannopyranosyl-(2S,3R)-erythritol of conventional MELs. Furthermore, these new glycolipids possessed both short-chain acids (C2 or C4) and long-chain acids (C14, C16, or C18) on the mannose moiety. The major component of the present glycolipids clearly showed different interfacial and biological properties, compared to conventional MELs comprising two medium-chain acids on the mannose moiety. Accordingly, the novel MEL diastereomers produced by P. crassa should provide us with different glycolipid functions, and facilitate a broad range of applications of MELs.

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