Characterization of a novel lipopolysaccharide biosurfactant from Klebsiella oxitoca

The chemical, physical, and emulsifying properties of BSF-1, which is an extracellular lipopolysaccharide biosurfactant produced by Klebsiella oxytoca strain BSF-1, were studied. BSF-1 was found to be composed mainly of carbohydrate and fatty acids. The average molecular weight was 1,700-2,000 kDa. The polysaccharide fraction contained L-rhamnose, D-galactose, D-glucose, and D-glucuronic acid at a molar ratio of 3:1:1:1. The fatty acid content was 1.1% (w/w) and consisted mainly of palmitic acid (C16:0), 3-hydroxylauric acid (3-OH-C12:0), and lauric acid (C12:0). In terms of thermal properties, BSF-1 was revealed to have inter- and intra-molecular hydrogen bonds. The hydrodynamic volume (intrinsic viscosity) of BSF-1 was 22.8 dL/g. BSF-1 could be maintained as a stable emulsion for 48 h through a low-level reduction in surface tension. The optimal emulsification temperature was 30 °C. Emulsification by BSF-1 was efficient at both acidic and neutral pH values.