Isolation and characterization of two new lipopeptide biosurfactants produced by Pseudomonas fluorescens BD5 isolated from water from the Arctic Archipelago of Svalbard

Abstract

The arctic freshwater bacterium Pseudomonas fluorescens BD5 produces biosurfactants when grown on 2% glucose. Crude biosurfactants were extracted from a cell-free culture supernatant with ethyl acetate and purified by preparative reversed phase high performance liquid chromatography (RP-HPLC). The chemical structure of the purified biosurfactants, pseudofactin I and II, was analyzed by matrix assisted laser desorption/ionization time of flight (MALDI TOF) mass spectrometry and tandem mass spectrometry (MS/MS). Both compounds are novel cyclic lipopeptides with a palmitic acid connected to the terminal amino group of eighth amino acid in peptide moiety. The C-terminal carboxylic group of the last amino acid (Val or Leu) forms a lactone with the hydroxyl of Thr3. Pseudofactin II reduced the surface tension of water from 72 mN/m to 31.5 mN/m at a concentration of 72 mg/l. Its emulsification activity and stability was greater than that of the synthetic surfactants Tween 20 and Triton X-100; pseudofactins thus have a great potential for application in industrial fields such as bioremediation or biomedicine.