Analysis of structural modifications and metagenomic sequencing during the ensiling of Caragana korshinskii provides insights into how extrusion pretreatment promotes lignocellulose degradation

In this study, to address the problems of poor silage fermentation quality and difficulty degrading lignocellulose interfering with resource utilization of Caragana korshinskii biomass, the effects of extrusion pretreatment (temperature 140°C and screw speed of 400 rpm) on its ensiling process were investigated. Results showed that pretreatment significantly improved silage quality, with lactic acid and water-soluble carbohydrate content increasing significantly ( P < 0.05), neutral detergent fiber content decreasing significantly ( P < 0.05), and hemicellulose degradation rate increasing by 31.64 ± 1.20% compared with the normal silage group. Microstructure analysis showed that pretreatment destroyed the dense biomass structure, increased specific surface area and porosityenhanced hydrophilicity, and reduced crystallinity, thus promoting the degradation of hemicellulose and cellulose. Metagenomic analysis further showed that extrusion pretreatment remodeled the microbial community structure, increasing the proportion of lactic acid bacteria such as Weissella and Companilactobacillus , and significantly increased the abundance of genes encoding debranching enzymes (CE3 and CE12) involved in hemicellulose degradation as well as main chain hydrolases (GH43 and GH8) ( P < 0.05). This study provides insights into the mechanisms by which extrusion pretreatment improves Caragana korshinskii silage in terms of physical and chemical structure and microbial functions, and this in turn may provide a technical and theoretical basis for understanding how efficient ensiling can be achieved more broadly in high-lignocellulosic feedstocks.