Degradation of alicyclic molecules by Rhodococcus ruber CD4

The present work describes investigations on the bacterial degradation of t he alicyclic molecule cyclododecane. It represents a structure where the in itial degradative steps have to be similar to a "subterminal" attack as the re is no "terminal" part of the molecule. We were able to show that the gra m-positive bacterium Rhodococcus ruber CD4 DSM 44394 oxidizes cyclododecane to the corresponding alcohol and ketone, the latter being subject to ring fission by a Baeyer-Villiger oxygenase. This key enzyme is an NADPH- and O- 2-dependent flavoprotein with a substrate specificity for bigger rings. The further metabolism of the resulting lactone gives rise to an omega-hydroxy alkanoic acid that is susceptible to common beta-oxidation. Due to its alic yclic character and its ring size, cyclododecane is comparable to aliphatic bridge components that are an important element in the coal texture. They contribute to the three-dimensional coal structure and thus could serve as a valuable target for the oxidative abilities of R. ruber CD4 to reduce the molecular mass of coal.