A putative transporter gene PtMMF1 -deleted strain produces mono-acylated mannosylerythritol lipids in Pseudozyma tsukubaensis

Mannosylerythritol lipids (MELs) are glycolipid biosurfactants produced by various yeasts. Mmf1, a putative transporter of MELs, is conserved in the MEL biosynthesis gene clusters of diverse MEL producers, including the genera Ustilago , Pseudozyma , Moesziomyces , and Sporisorium . To clarify the function of Mmf1, we generated the gene-deleted strain of P. tsukubaensis Δ PtMMF1 and evaluated its MEL production. Using thin-layer chromatography analyses, we detected most MELs produced by Δ PtMMF1 in the culture supernatant. The spot size of diacylated MEL-B (the only product of the parental strain) was significantly smaller for strain Δ PtMMF1 than for the parental strain, and a mono-acylated MEL-D spot was detected. In addition, an unknown glycolipid was detected in the sample extracted from strain Δ PtMMF1 . Liquid chromatography–mass spectrometry and nuclear magnetic resonance analyses revealed that the unknown glycolipid was a novel MEL homologue, mono-acylated MEL-B. Key points • P. tsukubaensis is able to secrete MELs without PtMMF1p. • Strain ΔPtMMF1 mainly produced mono-acylated MELs.