CHANGES IN IN-VITRO DIGESTIBILITY OF ORANGE PEELS AND DISTILLERY GRAPE STALKS AFTER SOLID-STATE FERMENTATION BY HIGHER FUNGI

In-vitro digestibility of orange peels (OP) and distillery grape stalks (GS) was examined after solid-state fermentation by the basidiomycetes Pleurotus ostreatus, Agrocybe aegerita, and Armillariella mellea. The results obtained with these substrates, alone or mixed together, were compared with those from fermentation of wheat straw (WS). The digestibility of GS was enhanced by the solid-state growth of P. ostreatus (+16.22%) and A. aegerita (+4.24%); no improvement was obtained with A. mellea. The in-vitro-digestibility values of OP and OP + GS were similar to or lower than those of the unfermented substrates, and the only advantage observed was the loss of lignin content and a slight increase of crude protein in the end-products.