FIGURE 6.

Characterization of the biosurfactant produced by the strain CIG-6A^T using LC-MS in positive electrospray ionization mode (+ ESI). (A) MS showing the sodiated adducts of diacetylated acidic sophorolipids (AS) with hexadecanoic acid (C_16:0) lipid side chain at m/z values 678 and 700. (B) Diacetylated lactonic form of hexadecanoic acid (C_16:0) chain was detected at m/z 660. (C) The ion at m/z 492 and 536 corresponds to lactonic sophorolipid with decanoic acid and tridecanoic acid, respectively with lipid chain (LS-C_10:1 and LS-C_13:0). Two sodiated adducts of lactonic sophorolipid with pentadecanoic acid and octadecanoic acid, respectively with lipid chain (LS-C_15:3 and LS-C_18:2) were detected. Diacetylated sodiated adduct of sophorose moiety was observed at m/z 448 (D) Sodiated sophorolipid with the acidic and lactonic form with a decanoic fatty acid side chain (AS-C_10:2) was observed at m/z 530 and 512, respectively. (E) LC-MS spectra of the standard sophorolactone (SL-S), 1,4″-sophorolactone 6′,6″-diacetate in positive electrospray ionization mode (+ ESI). MS showing the protonated ion and sodiated adducts of di-acetylated lactonic sophorolipids (Ac₂LS) with octadecenoic (C_18:1) lipid side chains at m/z values 688 and 710, respectively.