The increasing environmental pollution is causing dramatic changes in the ecosystem. The search for solutions to this problem includes the development of new materials using more sustainable resources and processes, the development of biodegradable materials and the use of natural additives to tune the biodegradability of these materials. At the same time, nature finds its way to adapt to the environmental changes. In particular, microorganisms have the capacity to adapt fast to these changes. In this chapter, microorganisms (fungi and bacteria) able to trigger biodegradation of polymeric materials, particularly plastics, and the relevant physico-chemical mechanism (enzymatic activity, pH, temperature, etc.,) involved in the biodegradation process are described.