Chemical Structure of Lipid Bioflocculant Produced by Rhodococcus erythropolis

Abstract

We have identified the chemical structure of the lipid bioflocculant produced by Rhodococcus erythropolis S-1 strain. It was hydrolyzed with alkali and decomposed to sugar and fatty acid fractions. The sugar fraction was identified as a mixture of glucose and trehalose by HPLC and TLC analyses combined with acid and enzyme hydrolyses. The fatty acid fraction was identified as a mixture of many molecular classes of mycolic and mycoleic acids (2-alkyl-3-hydroxy long-chain fatty acids) of which the molecular masses were from 496 to 606 (C₃₂-C₄₀) with GC-MS analysis after methylesterification and trimethylsilylation. A gel permeation column chromatography study suggested that the lipid bioflocculant contained trehalose monomycolate, glucose monomycolate, and trehalose dimycolate. Furthermore, we showed that the lipid bioflocculant can be extracted directly from Rhodococcus erythropolis S-1 cells with organic solvents such as ethanol.