Olive Cake (OC) generated by the olive oil industries, well implanted in Tunisia, represents a major disposal
and potentially severe pollution problem. This work presents the study of bioconversion of OC in
solid state fermentation with the medicinal mushroom, Fomes fomentarius so as to upgrade its nutritional
values and digestibility for its use as ruminants feed. The fungus was cultured on OC for 7–30 d, and subsequently
the chemical composition, lignocellulolytic enzyme activities and in vitro digestibility of the
resultant substrate were determined. The results obtained showed an increase in the crude protein ranging
from 6% to 22% for the control and for treated OC, respectively. Significant (P < 0.05) decreases in the
values of neutral detergent fiber (hemicelluloses, cellulose and lignin), acid detergent fiber (lignin and
cellulose) and acid detergent lignin were detected (23%, 13% and 10%, respectively). The estimated
in vitro digestibility improved from 9% (control) to 25% (treated OC). The present findings revealed F.
fomentarius to be an efficient organism for lignocellulolytic enzymes production and simultaneous
enhancement in crude protein and in vitro digestibility of OC.