An alkaline peroxide industrial pulp from poplar was treated with a manganese peroxidase (MnP) from the hypersecretory strain of Phanerochaete chrysosporium 1-1512 after a second stage of refining. The enzymatic treatment caused an improvement in the pulp quality by inducing an enzymatic refining onto the fibers. Transmission electron microscopy showed that the enzymatic refining was characterized by internal. and external fibrillation of the fibers. Chemical modifications of lignin caused by MnP treatment facilitated the post-refining stage before papersheet manufacture. All together the enzymatic treatment resulted in energy savings of 25% during beating.