Effect of biological lignin depolymerization on rice straw enzymatic hydrolysis, anerobic fermentation...

This study investigated the effects of lignin depolymerization using laccase on rice straw silage fermentation characteristics, lignocellulose biodegradation and in vitro digestibility. Rice straw was ensiled for 120 days, either without additives (control), or pretreated with Lactobacillus plantarum and cellulases (LPC), cellulases and laccase (CL), and L. plantarum, cellulases and laccase (LPCL). The results revealed that LPC and LPCL treated silages exhibited significantly lower (P < 0.05) pH values, higher (P < 0.05) lactic acid content (24.76 and 27.02 g/kg dry matter (DM)) and significantly higher water-soluble carbohydrate content (20.12 and 22.46 g/kg DM) compared to control and CL treated silages. Laccase-containing treatments (CL, LPCL) significantly reduced lignin, cellulose and hemicellulose contents in the ensiled rice straw compared to the control and LPC treated silages. Structural alterations in the straw, induced by pretreatments, were confirmed by Fourier Transform Infrared spectroscopy, Scanning Electron Microscope and X-ray diffraction analysis. The CL treated silage exhibited the lowest (P < 0.05) in vitro digestibility, while the LPCL treated silage had the highest in vitro total gas production (25.50 mL). In conclusion, laccase effectively degraded lignin during ensiling, and the combined application of laccase with L. plantarum and cellulases enhanced both the enzymatic hydrolysis and ensiling quality of rice straw. These findings demonstrate the potential of biological lignin depolymerization during ensiling as an innovative strategy to significantly enhance the nutritional value of straw bioresources, paving the way for sustainable livestock production and waste reutilization.