Artifactual origin of mycobacterial bacteran. Formation of melanoidin-like artifact macromolecular material during the usual isolation process

Three species of mycobacteria are shown to afford quite a high level of insoluble, non-hydrolysable (INH) material when subjected to usual drastic saponification and acid hydrolysis. The spectroscopic features (FTIR, solid-state C-13 NMR), the thermal behaviour (DTG analysis) and the chemical degradation products (alkaline KMnO4 oxidation) of these materials are compared with those of melanoidin-like polymers synthesized from a mixture of monosaccharides and amino acids occurring in the mycobacterial cell walls. The mycobacterial INH materials, thus, appear to correspond to artifacts generated during the isolation process. The implication of these results, on the contribution of such melanoidin-like artifact macromolecular materials in the INH residues previously isolated from other microorganisms is discussed. A new process of isolation avoiding the formation of such artifacts is proposed. (C) 1997 Elsevier Science Ltd.