1,2† 1Department of Agrobiotechnology IFA-Tulln, Institute of Environmental Biotechnology, University of Natural Resources and Life Sciences, Vienna, Austria 2Division Polymers & Enzymes, Austrian Centre of Industrial Biotechnology, Graz, Austria 3Institute of Microbiology and Microbial Biotechnology, University of Natural Resources and Life Sciences, Vienna, Austria 4Department of Material Sciences and Process Engineering (MAP), Institute of Physics and Materials Science (IPM), Vienna, Austria 5Department of Microbiology, University of Innsbruck, Innsbruck, Austria Microorganisms, like bacteria and fungi, are becoming an emerging resource for the development of eco-sustainable plastic degradation and recycling processes. In this study, the rumen content from cattle ( Bos taurus) was investigated regarding synthetic polyester hydrolyzing enzymes based on the fact that the diet of ruminants may contain natural plant polyesters. A screening with model substrates demonstrated hydrolytic activities of rumen fluid on