Effects of phenolic-rich agro-industrial by-product supplementation on yield, nutritional content and antioxidant capacity of Pleurotus djamor

Abstract

Wheat bran is widely used as a supplement in Pleurotus cultivation, but it can be costly and not always available, prompting nutrient and bioactive-rich alternatives. In this study, four phenolic-rich residues, used tea leaves, olive press cake, grape pomace, and green walnut hulls, were used as supplements to wheat straw in the cultivation of Pleurotus djamor, and the effects of the cultivation substrates on yield, biological efficiency, nutritional composition, total phenolic content, antioxidant activity, and Fourier-transform infrared spectroscopy-derived functional group profiles were determined. Adding 20% used tea leaves increased total yield by 34% to 213.0 g/kg; olive press cake accelerated mycelial growth (15 d) and shortened harvest time (23.6 d). Mushrooms contained 15.17–26.25 g/100 g protein and 72.17–74.81 g/100 g carbohydrate and 1.24–1.56 g/100 g fat on a dry-weight basis. Total phenolic content correlated positively with antioxidant activity, and the control showed the highest values. FTIR spectra indicated substrate-dependent shifts. Overall, phenolic-rich supplements can improve performance and shape composition, but they do not consistently raise fruiting body total phenolic content or antioxidant levels; used tea leaves appear the most promising substrate for P. djamor cultivation.