Molecular evidence for biodegradation of geomacromolecules

The biodegradability of macromolecular organic structures of geological ori gin was investigated by performing in vitro studies. Cultures of the common Nocardioides simplex were grown, first, on a high molecular weight, asymme tric thioether (1-(phytanylsulfanyl)-octadecane 1) and then on macromolecul ar fractions isolated from a sulfur-rich oil. Gross data indicate that bact eria convert macromolecular substances to material of higher polarity by ox idizing the abundant thioethers to sulfones and sulfoxides and by introduci ng new functionalities, such as carboxylic acid, keto or hydroxyl groups. F urthermore, bacteria remineralize the macromolecular structures. Bacterially induced alterations were also studied on a molecular level afte r chemical desulfurization of the macromolecular structure. Thus, it could be established that the amounts of linear hydrocarbons in the macromolecula r structure are decreased relative to branched and cyclic structures due to a preferential bacterial attack of the linear moieties bound to the macrom olecules. This is further supported by the detection of S-bound fatty acids resulting from the bacterial oxidation of S-bound n-alkanes. Moreover, N. simplex also degraded sulfur-bound steranes by oxidation of the steroid sid e-chain leading to S-bound steroid acids. Copyright (C) 2000 Elsevier Scien ce Ltd.