Improving the nutritive value of Olive Cake by solid state cultivation of the medicinal mushroom Fomes fomentarius

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.

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► Solid state bioconversion of Olive Cake into a value added animal feed is proposed.
► Fomes fomentarius possesses an efficient ligninocellulolytic system.
► Solid state fermentation decreases the fiber contents of Olive Cake.
► A significant increase in protein content of treated Olive Cake is obtained.
► Solid state fermentation improves the estimated in vitro digestibility of Olive Cake.