Solid state fermentation of orange peel and grape stalks by Pleurotus ostreatus,Agrocybe aegerita,and Armillariella mellea

Summary Solid state cultures of Pleurotus ostreatus, Agrocybe aegerita, and Armillariella mellea were carried out on orange peel (OP) and distillery grape stalks (GS), single or mixed, and compared with that on wheat straw (WS). Good levels of substrate colonization were achieved on OP and GS by P. ostreatus and A. aegerita, whereas A. mellea was grown on OP alone or mixed with GS. A. aegerita completed its life cycle producing basidiocarps on all substrates, while P. ostreatus fruited only on WS and OP+GS. A. mellea did not produce basidiocarps during the experiment. Indeed, P. ostreatus and A. aegerita depleted 50%–60% and 20%–30% of the lignin content, respectively, for OP and GS, while A. mellea degraded 22% of lignin only on GS. The latter fungus utilized only water soluble sugars on OP and OP+GS and so it would not be suitable for direct bioconversion of these raw materials. The results obtained, compared with those of the WS fermentation process, suggest the possibility of utilizing such lignocellulosic substrates as ruminant feed.