Biological delignification and anaerobic fermentation of wheat straw: A promising approach for sustainable utilization of crop straw bioresources

Agricultural crop residues, such as wheat straw, represent a renewable and valuable bioresource. However, their utilization is often constrained by the recalcitrant structure, primarily due to severe lignification, leading to resource wastage and environmental pollution. This study offers a promising approach for the hygienic preservation and efficient utilization of wheat straw through laccase mediated delignification. The effects of laccase pretreatment on anaerobic preservation, structural composition, biodegradation, and in vitro digestibility were investigated. Wheat straw was ensiled for 120 days after four pretreatments: untreated (control), or pretreated with Lactobacillus plantarum and hemicellulase (LPH), hemicellulase and laccase (HL), and a combination of L. plantarum, hemicellulase and laccase (LPHL). Laccase pretreatment significantly degraded lignin, enhancing cellulose and hemicellulose hydrolysis. The LPHL pretreatment significantly reduced silage pH (<4.10) and lignin content, and preserved higher (p < 0.05) concentrations of water-soluble carbohydrates (15.06 g/kg dry matter). Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction confirmed substantial physico-chemical alterations in silage composition, particularly in HL and LPHL treated groups. Notably, HL treatment improved in vitro neutral detergent fiber (36.56 %) and acid detergent fiber (37.91 %, p < 0.05) degradation. Moreover, delignified silage (HL and LPHL) resulted in higher (p < 0.05) in vitro gas production (36.67 and 39.33 mL). Overall, the synergistic application of laccase and lactic acid bacteria effectively reduces lignin, promotes enzymatic hydrolysis, and offers a sustainable strategy for the valorization of crop residues in ruminant nutrition and value-added product development.