Selective production of deacetylated mannosylerythritol lipid, MEL-D, by acetyltransferase disruption mutant of Pseudozyma hubeiensis.

Mannosylerythritol lipids (MELs) are produced by several smut fungi of the Ustilaginaceae family; they are promising microbial biosurfactants and have excellent surface-active and self-assembling properties. Pseudozyma hubeiensis is a candidate for abundant MEL production and produces large amounts of 4- O -[(4′-mono- O -acetyl-2′,3′-di- O -alkanoyl)-β- d -mannopyranosyl]- meso -erythritol (MEL-C). An acetyltransferase disruption mutant of P. hubeiensis , SY62-MM36, was obtained to selectively produce deacetylated 4- O -[(2′,3′-di- O -alkanoyl)-β- d -mannopyranosyl]- meso -erythritol (MEL-D), and the structures of the products were determined. Lower mobility of major spots of the mutant on silica gel thin-layer chromatography verified its more hydrophilic nature than that of wild-type MEL-A, B, and C. Structural analyses confirmed the product to be MEL-D, which comprises acyl chains of caproic acid (C6:0), capric acid (C10:0), and lauric acid (C12:0). The critical micelle concentration (CMC) and the surface tension (γCMC) of the MEL-D were 2.0 × 10 −5 M and 29.7 mN/m, respectively. SY62-MM36 also produced a minor product that was estimated as triacylated MEL-D. The triacylated MEL-D had a CMC of 3.5 × 10 −5 M and a γCMC of 29.6 mN/m. In water, MEL-D formed a lamella liquid crystal phase over a broad range of concentrations. By fed-batch cultivation, the mutant produced 91.6 ± 6.3 g/L of MEL-D for 7 days. [ABSTRACT FROM AUTHOR]