Exploring the Potential of Epiphytic Microbiota and Plant-Derived Cellulolytic Enzymes for Efficient Lignocellulose Degradation

Lignocellulose, the most abundant biomass resource on Earth, faces significant technological and economic challenges in biorefining. Solid-state fermentation (SSF) offers a promising approach for its efficient utilization; however, the degradation mechanisms remain poorly characterized. Here, we employed electron beam sterilization, high-temperature enzyme inactivation, and organic acid simulation to design four treatments: (1) epiphytic microbiota + sterilized alfalfa (CK); (2) epiphytic microbiota + sterilized and enzyme-inactivated alfalfa (EM); (3) sterilized water + sterilized alfalfa (CE); and (4) sterilized organic acid mixture + sterilized and enzyme-inactivated alfalfa. After 60 days, scanning electron microscopy (SEM) revealed substantially more severe surface structural damage in EM compared to CE. Furthermore, the OA had lower lignocellulose content (376 g/kg dry matter, DM) and higher glucose (8.09 g/kg DM) release than that of CE (lignocellulose, 380 g/kg DM; glucose, 3.39 g/kg DM). The exclusive detection of cellobiose in CE indicated distinct cellulose degradation mechanisms between CE and OA. Analysis of hemicellulose-derived monosaccharides showed that xylose, galactose, and arabinose were preferentially released. Correlation analysis identified Lactiplantibacillus plantarum, Lactiplantibacillus pentosus, Weissella cibaria, and Pediococcus pentosaceus as key taxa negatively correlated with hemicellulose content. This study provides critical insights into lignocellulose degradation dynamics during SSF, which informs strategic designs for enhanced biomass valorization.