Characterization of ligninolytic enzyme production in white-rot wild fungal strains suitable for kraft pulp bleaching.

Fungal strains identified by phylogenetic analysis of the ITS rDNA region as (CMU-TA01), (CMU-84/13), and sp. (CMU-47/13) are able to grow on and bleach kraft pulp (KP) in a simple solid-state fermentation (SSF) assay conducted in Petri dishes. Kappa number reductions obtained with sp. (48.3%), (43%), and . (39.3%), evidence their capability for lignin breakdown. Scanning electron microscopy images of KP fibers from SSF assays demonstrated increased roughness and striation, evidencing significant cell wall modification. produces laccase (Lac), manganese peroxidase (MnP), and lignin peroxidase (LiP) in potato dextrose broth (PDB), PDB + CuSO, and PDB + KP, whereas sp. and showed no Lac and low LiP activities in all media. Compared to PDB, the highest increase in Lac (7.25-fold) and MnP (2.37-fold) activities in PDB + CuSO occur in ; for LiP, the greatest changes (6.95-fold) were observed in . Incubation in PDB + KP shows significant increases in Lac and MnP for , MnP and LiP for sp., and none for . SSF assays in Petri plates are a valuable tool to select fungi that are able to delignify KP. Here, delignification by sp. of this substrate is reported for the first time, and MnP activity was strongly associated with the delignification ability of the studied strains. The obtained results suggest that the studied fungal strains have biotechnological potential for use in the paper industry.