In this thesis (R)-3-hydroxycarboxylic acids (HA) from bacterial polyhydroxyalkanoates (PHA) were investigated, regarding their biotechnological production as well as intracellular processes of their formation and degradation. An innovative bioprocess to provide HA as fine chemicals for further applications is presented. The method is straightforward, easy to handle and results in high yields (introduced in chapters 2-4). Following the observations of this study, attempts to scale up the process seemed possible and potential applications of HA remain topics of research. The underlying mechanisms of PHA degradation were also addressed, including issues of physiological advantages of HA excretion for cells (chapter 5) and characterization of enzymes having HA as substrates (chapters 6 and 7). Even though some aspects of PHA metabolism were clarified for P. putida GPo1, many details about intracellular PHA degradation remain obscure and require further experiments and discussion. Knowledge about their molecular context in the bacterial cell is crucial for efficient PHA and HA production.