Thermogravimetry, differential scanning calorimetry, and wide-angle X-ray scattering techniques were used to study changes in the composition, relative heat of fusion, and mean crystal size of blends made from low-density polyethylene (LDPE) and sugar cane bagasse (SCB), before and after exposure to the fungus Phanerochaete chrysosporium for 32 days. The initial blends contained equal weights of each component. The composition of the blend LDPE/SCB at 32 days changed to the value (66 +/- 3)/(34 +/- 3). The relative heat of fusion of LDPE increased during the first 16 days, but then it showed a tendency to decrease and remain constant. The estimated mean crystal size of polyethylene decreased but then remained almost constant. These changes indicate that the microorganisms mainly digest SCB in the first stage of the experiment, but later they also digest LDPE. The crystalline morphology of the LDPE is modified; the crystalline domains are divided into smaller crystallites.