Sterilization strategy determines degradation efficacy of diverse lignocellulosic biomasses by Irpex lacteus

Biological pretreatment by white-rot fungi is a promising green technology for lignocellulose valorization, yet its industrial application is hampered by the high energy consumption of conventional steam sterilization. While a hurdle technology strategy combining low-temperature pasteurization and pH control has proven effective for wheat straw, its general applicability across diverse agricultural residues remains unclear. This study systematically compared the effects of low-temperature pasteurization (70 °C and 80 °C) with autoclaving (121 °C) on the pretreatment of wheat, rice, and rapeseed straw by Irpex lacteus at an initial pH of 4.5. The results revealed significant substrate-specific responses. For wheat and rapeseed straw, pasteurization achieved enzymatic saccharification yields comparable to or exceeding those of autoclaving, demonstrating excellent energy-saving potential. In contrast, rice straw required autoclaving at 121 °C to achieve maximum delignification (55.91% acid-insoluble lignin loss) and subsequent sugar release, likely due to its more recalcitrant native microbiota and structure. Pyrolysis-Gas Chromatography-Mass Spectrometry (Py-GC/MS) analysis confirmed that the S/G ratio decreased after pretreatment. Correlation analysis further established that the S/G ratio had a stronger negative correlation with glucose yield (r = - 0.94) than the total acid-insoluble lignin (AIL) content (r = - 0.90). These results suggest that the selective degradation of lignin structure, particularly the removal of S-units, is more closely associated with hydrolysis efficiency than total lignin removal. This work validates the viability of a low-temperature biological pretreatment strategy and underscores the necessity of tailoring protocols to specific feedstock characteristics to achieve efficient and economical biomass conversion.