Improving the nutritional value of button mushroom (Agaricus bisporus) through cornmeal supplementation in compost and peat substitution in casing soil

• Recycled casing soils and compost supplements supported sustainable mushroom growth. • Recycled casing soils had the potential to perform similarly to commercial ones. • Cornmeal-supplemented compost improved nutritional quality more than casing soils. • Recycled casing soils and compost supplements reduced reliance on commercial soils. The cultivation of Agaricus bisporus, widely known as the white button mushroom, constitutes a significant global agricultural industry due to its nutritional and health benefits. This study evaluated alternative casing soil formulations using recycled materials and sugarcane bagasse to partially replace peat, thereby improving the yield and nutritional quality of A. bisporus. Additionally, the effects of cornmeal (CM) supplementation to the compost were evaluated on various mushroom characteristics. Results indicated that CM supplementation had stronger positive effects than casing soil treatments on first flush yield, antioxidant enzyme activities, phenolics, DPPH activity, protein content, and N and Mg levels in mushrooms. Among the treatments, the C3 casing soil—composed of 20 % BVB™ substrate, 40 % recycled soil, 25 % fresh sugarcane bagasse, 10 % fermented sugarcane bagasse, and 5 % CaCO₃ + perlite—combined with S2 (1000 g m −2 CM) supplementation, resulted in the highest mushroom firmness (3.45), representing a 40.8 % increase compared with the control (2.45). It also showed a 23.91 % increase in dry weight relative to the control (6.79 vs. 5.48 %), while maintaining a comparable fiber content (10.67 vs. 10.69 % DW). The highest protein content (3.88 % FW) was obtained with the peat substrate at the S3 (1500 g m −2 CM) supplementation level, representing a 14.12 % increase compared with the control (3.40 % FW), followed by S3C3. In C3 casing soil, mushrooms exhibited comparable DPPH, GPOX, and total phenol contents to those grown in peat (C2) at S2 and S3 supplementation. These findings indicate that the C3 casing soil can replace the tested commercial substrates.