Utilization of spent substrates and waste products of mushroom cultivation to produce new crops of Pleurotus ostreatus, Pleurotus eryngii and Agaricus bisporus

Five agro-industrial residues, their corresponding spent mushrooms substrates (SMS), commercial fresh and spent mushroom compost of Agaricus (SMC) and Pleurotus ostreatus (SMS GZ) cultivation, Pleurotus and Agaricus waste (stipes/mishappen mushrooms) were combined and re-utilized as novel substrates for the cultivation of P. ostreatus, P. eryngii and A. bisporus mushrooms. SMSs/ SMC were used up to 40% (treatment 1 and 2), while 20% of mushroom waste were added in fresh and spent substrates (treatment 3 and 4). The impact of different substrates on mycelial growth rate and biomass production was examined. Then, Pleurotus spp. were cultivated on the most promising substrates and essential cultivation aspects (earliness, total mushroom yield, biological efficiency-BE) and carposomes’ quality parameters (weight, morphological characteristics) were evaluated. Laccase and endoglucanase production by Pleurotus species were also determined at 50 and 100% of colonization stages. All species showed their fastest mycelial growth rate (up to 5 mm/day) on substrates consisted of SMC, whereas many combinations of species/substrate enhanced biomass production. The SMS GZ supplementation positively affected laccase activity; in the cultures of P. ostreatus and P. eryngii the highest values were 62,539 U/g d.w. and 17,584 U/g d.w., respectively. On the contrary, small amounts of endoglucanase were produced (0.007 to 0.322 U/g d.w.); the greatest production was recorded for P. ostreatus at full colonization. Regarding fermentation in bags, significant amount of total mushroom yield was produced in all substrates and those with SMS GZ supported the fastest earliness period and the highest BE for both Pleurotus species. BE values ranged from 54 to 133% for P. ostreatus and from 53 to 121% for P. eryngii. Concerning morphological characteristics, mushroom waste addition seemed to affect them positively. The data included in this paper support the effective re-utilization of different types of SMS and mushroom waste for fungal mass and enzymes’ production and for new high quality Pleurotus spp. carposomes.