Optimization of Agro-Residue Substrates for Sustainable Cultivation of Pleurotus giganteus in Hainan, China

Pleurotus giganteus, a heat-tolerant mushroom with high nutritional and medicinal value, is a promising species for tropical mushroom cultivation in Hainan, China. However, its current dependence on rubber sawdust as the primary substrate compromises environmental sustainability. In this study, we applied a “replacing wood with grass” strategy and used a simplex-lattice design to optimize substrate formulations based on agro-residues. Laboratory screening identified banana straw and chili straw as effective substitutes for rubber sawdust, supporting rapid and dense mycelial growth. Mixed formulations showed distinct advantages in mycelial growth, enzyme activity, agronomic traits (growth cycle, yield, and cap-to-stipe ratio), and nutritional composition compared to the control formulation (CF), particularly in terms of growth rate and laccase activity. Correlation analyses revealed that both individual ingredients and their interactions significantly affected mycelial growth and agronomic traits, with the magnitude and direction of effects depending on their relative proportions. Based on expected response values for key evaluation indices, an optimal formulation (9.97% rubber sawdust, 24.33% banana straw, 10.70% chili straw, 40% cottonseed hulls, 10% wheat bran, and 5% lime) was predicted and experimentally validated to outperform the CF. This study provides a sustainable basis for localized cultivation of P. giganteus in Hainan and supports the high-value valorization of agricultural residues for mushroom production.