The betaproteobacteria Castellaniella defragrans 65Phen and Thauera linaloolentis 47Lol were recently isolated on monoterpenes as sole carbon and energy source under denitrifying conditions. C. defragrans 65Phen metabolizes the hydrocarbon monoterpene beta-myrcene. Its activation is catalyzed by the bifunctional enzyme linalool dehydratase/isomerase. In the presented work, an improved purification protocol was developed to yield high amounts of protein for structural analysis by X-ray crystallography. The structure of the enzyme and a proposed mechanism are described. T. linaloolentis 47Lol uses the tertiary monoterpene alcohol linalool as sole carbon source. It is isomerized into the primary alcohol geraniol by the enzyme linalool isomerase. The presented work describes an enrichment of the enzyme from protein extracts and its characterization. Further degradation of geraniol via the acyclic terpene utilization pathway was shown by cultivation based and enzymatic experiments