Research on the process of synergistic degradation of corn straw by probiotics—enzymes based on microbiome and metabolomics

Probiotics enzyme co-fermentation significantly improves the use efficiency and nutritional value of crop straw, although the underlying synergies are not clear. The experiment used corn straw as the raw material. It was treated with a 0.2% composite enzyme preparation containing cellulase, xylanase, lignin peroxidase, manganese peroxidase, and laccase. A composite microbial inoculant was also added at a total inoculum level of 1 × 10⁸ CFU/g, using a ratio of Lactobacillus, yeast, and Bacillus subtilis of 3:2:1. After thorough mixing, the solution was sprayed evenly onto the straw surface. Fermentation proceeded under room temperature conditions. Multipoint random sampling was carried out on days 7, 14, 21, and 28. By integrating metagenomic, metabolomic, and conventional analytical approaches, this study systematically investigated microbial community structure, dynamic metabolic pathways, and fermentation quality during the process. The application of a probiotics-enzyme composite led to a clear improvement in fermentation quality. It also reduced the cellulose content of corn stover compared to the untreated control. The results showed that major microbial taxa, such as Proteobacteria and Firmicutes, are influenced by environmental factors like pH and lactic acid. These microbes significantly degraded fibre components (p < 0.05) by secreting extracellular enzymes and organic acids. This process encouraged the accumulation of raw proteins and dipeptides. Key metabolic pathways, such as pyrimidine metabolism and the TCA cycle, were significantly enhanced. This led to the synthesis of valuable metabolites, including mevalonate and biopterin, which have increased antioxidant and metabolic properties. The research results demonstrate that the “microbiota structure—metabolic function—fermentation quality” relationship constitutes a complex and mutually influential system, providing important theoretical support for targeted microbial community regulation and optimization of fermentation processes in straw.