Recycling biotoxic green walnut husks through mushroom cultivation and impact of these wastes on yield and nutritional composition of Pleurotus spp.

The aim of the study was the bioconversion of green walnut husk (GWH) to nutrimental foods through mushroom cultivation technology. Two isolates of Pleurotus ostreatus and three isolates of Pleurotus eryngii cultivated in four different growing media supplemented different ratios of GWH were investigated for cultivation cycle, yield, biological efficiency (BE), fruiting body properties and nutritional composition of Pleurotus spp. In the study, poplar sawdust (PS) was used as a base substrate, and GWH were added at the ratios of 9:1, 8:2 and 7:3 to prepare the growing media. The control medium was prepared using PS only. Although increasing the GWH content led to prolonged pinning and flushing times, the addition of GWH at 10–20% ratios had a positive impact on mushroom performance. The yield and BE (%) of P. ostreatus and P. eryngii isolates ranged between 120.2 and 230.0 g/kg and 40.1–74.2% BE and 121.8–222.5 g/kg and 40.6–76.2% BE, respectively, depending on the growing medium used. Moreover, the fruitbodies of both strains of P. ostreatus demonstrated significant increases in protein and fat content when produced on substrates containing GWH, especially at a 20% ratio in the growing medium. These results indicate that GWH, an agricultural waste that poses a risk to the environmental health, could be successfully used in the cultivation of both oyster mushroom species.