Abstract
Biosurfactants are surface-active compounds produced by microorganisms. Mannosylerythritol lipids (MEL) are promising biosurfactants produced by Ustilaginomycetes, and their physicochemical and biochemical properties differ depending on the chemical structure of their hydrophilic and/or hydrophobic moieties. To further develop MEL derivatives and expand their potential applications, we focused our attention on the use of cuttlefish oil, which contains polyunsaturated fatty acids (e.g., docosahexaenoic acid, C22:6, and eicosapentaenoic acid, C20:5, as the sole carbon source. Among the microorganisms capable of producing MEL, only nine strains were able to produce them from cuttlefish oil. On gas chromatography-mass spectrometry (GC/MS) analysis, we observed that Pseudozyma churashimaensis OK96 was particularly suitable for the production of MEL-A, a MEL containing hexadecatetraenoic acid (C16:4) (23.6% of the total unsaturated fatty acids and 7.7% of the total fatty acids). The observed critical micelle concentration (CMC) and surface tension at CMC of the new MEL-A were 5.7×10–6 M and 29.5 mN/m, respectively, while those of MEL-A produced from soybean oil were 2.7×10–6 M and 27.7 mN/m, respectively. With polarized optical and confocal laser scanning microscopies, the self-assembling properties of MEL-A were found to be different from those of conventional MEL. Furthermore, based on the DPPH radical-scavenging assay, the anti-oxidative activity of MEL-A was found to be 2.1-fold higher than that of MEL-A produced from soybean oil. Thus, the newly identified MEL-A is attractive as a new functional material with excellent surface-active and antioxidative properties.
