The present invention relates to a process for producing biodegradable polymeric materials including polyhydroxyalkanoates (PHAs) by using the cell debris left from PHA recovery and purification. The process comprises: (a) cultivating PHA-producing microbial cells in a medium solution containing an organic carbon source to form PHAs that are accumulated in the cells as inclusion bodies; (b) harvesting the cells from the spent medium and solubilizing the non-PHA cell mass to obtain a PHA solid and a cell debris solution; (c) separating the PHA solid from the cell debris solution; (d) feeding the cell debris solution to the cultivation step (a). By reusing the cell debris generated from PHA recovery, the invention avoids disposal of a large amount of aqueous waste. In addition, a remarkable increase of cell growth and PHA synthesis is achieved, because the cell debris can be readily assimilated by the microbial cells as the nutrients.