Effect of olive mill waste (OMW) supplementation to Oyster mushrooms substrates on the cultivation parameters and fruiting bodies quality

Seven Oyster mushroom strains were cultivated in wheat straw (WS) bags supplemented with 0 up to 90% olive mill waste (OMW), a solid residue obtained from a two-phases olive oil production system. All mushroom strains could grow but high OMW concentrations resulted in a significant yield, biological efficiency and productivity decrease, retarding of pinning and flushing and loss of fruiting bodies quality. However, most of the mushroom strains showed no significant differences on cultivation parameters and fruiting bodies quality (except for colour) between control (WS) substrates or substrates supplemented up to 50% OMW (w/w). Addition of 50% OMW to WS substrates turned mushrooms lighter and less reddish. This colour shift was not due to enzymatic oxidations or inhibition since laccase and peroxidase activities were not differing from control. Total phenolic content and antioxidant activity were also similar and no phenolic compounds from OMW were detected in the fruiting bodies. Some of the analysed Pleurotus strains were better suited to grow on OMW supplemented substrates than others.