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

Rhodococcus erythropolis DSM 432 15 produced a surface-active trehalose lipid whose formation was induced by n-alkanes to a maximum of 2.1 g 1-1 in a 50 1 batch culture on 2% (w/v) n-alkanes of chain length C13 to CIS. The glycolipid was extracted from the biomass with n-hexane and was purified by repeated chromatography on silica gel. It contained aptrehalose 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 a-branched P-hydroxy fatty acids (mycolic acids) ranging from C32H6403 to C38H7603, of which C34H,80, and C35H7003 predominated. The molar ratio of trehalose to mycolic acids was 1 : 2. 13C nuclear magnetic resonance analysis of the 0hexamethyltrehalose 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.