ELISABETA ELENA POPA, MARIA RAPA, CALINA PETRUTA CORNEA, VLAD IOAN POPA, AMALIA CARMEN MITELUT, OVIDIU POPA, MIHAELA GEICU CRISTEA, MONA ELENA POPA PHB/CELLULOSE FIBRES COMPOSITES COLONIZATION AND BIODEGRADATION BEHAVIOR In this study, newly developed polymeric composites based on poly(3-hydroxybutyrate) (PHB), cellulose fibres (CF) and plasticizer (bis<2-(2-butoxyethoxy)ethyl> adipate) (DBEEA) were subjected both to microorganism’s action in controlled conditions, and to soil’s action by sample burial. The weight loss of PHB based composites at 60 days exposure were determined in comparison with neat PHB. The weight variation for PHB based composites buried in a natural soil at 45 days and 90 days was monitored. DSC-differential scanning calorimetry and SEM -scanning electron microscopy analysis were performed on the tested composites after 90 days of soil burial. It was found that the introduction of cellulose fibres into PHB leads to the increase of biodegradability of composites.