Formation, Isolation and Characterization of Trehalose Dimycolates from Rhodococcus erythropolis Grown on n-Alkanes

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Abstract
Summary: Rhodococcus erythropolis DSM 43215 produced a surface-active trehalose lipid whose formation was induced by n-alkanes to a maximum of 2.1 g l-1 in a 50 l batch culture on 2% (w/v) n-alkanes of chain length C12 to C18. The glycolipid was extracted from the biomass with n-hexane and was purified by repeated chromatography on silica gel. It contained α,α-trehalose as the sole non-reducing sugar. The lipid moiety was characterized by 13C nuclear magnetic resonance spectroscopy and mass spectrometry and consisted predominantly of saturated long-chain α-branched β-hydroxy fatty acids (mycolic acids) ranging from C32H64O3 to C38H76O3, of which C34H68O3 and C35H70O3 predominated. The molar ratio of trehalose to mycolic acids was 1:2. 13C nuclear magnetic resonance analysis of the O-hexamethyltrehalose obtained by saponification of the permethylated trehalose dimycolates revealed, with the aid of deuterium exchange, that the ester linkages of mycolic acids are to both primary alcohol groups at the C-6 and C-6’ positions of the trehalose.