Optimizing fermentation quality via lignocellulose degradation: synergistic effects of fibrolytic additives and Lactiplantibacillus plantarum on Elymus dahuricus silage

The harsh environmental conditions on the Qinghai-Tibetan Plateau challenge forage preservation, necessitating resilient strategies for silage making. This study evaluated the effects of fibrolytic additives, alone or combined with Lactiplantibacillus plantarum, on fermentation quality, lignocellulose degradation, and microbial community of Elymus dahuricus silage. The Elymus dahuricus was ensiled with (1) distilled water (C), (2) formic acid (FA), (3) fibrolytic enzymes (FE), (4) fibrolytic microbial consortium (MC), and (5–8) combinations with L. plantarum (Lp) inoculants (CLp/FALp/FELp/MCLp) for 50 days. The results demonstrated that fibrolytic additives improved fermentation quality, evidenced by significantly (p < 0.05) higher lactic acid, dry matter and water soluble carbohydrate contents, and lower pH value and ammonia nitrogen contents. Fibrolytic additives significantly (p < 0.05) increased lignocellulose degradation, with SEM and FTIR analyses confirming structural disruption and chemical bond cleavage. The combination with Lp-inoculants further improved fermentation quality and lignocellulose degradation, with FELp demonstrating the highest lignocellulose degradation efficiency and optimal fermentation quality. Formic acid and fibrolytic enzymes established the dominance of L. plantarum by suppressing undesirable microbes and providing fermentable substrates, respectively. Fibrolytic microbial consortium increased the relative abundance of heterofermentative LAB (Lentilactobacillus buchneri and Levilactobacillus brevis) and cellulolytic bacteria (Bacillus subtilis and Enterococcus faecium). Combining fibrolytic enzymes with L. plantarum (FELp) presented the greatest lignocellulose degradation and optimal fermentation quality. Fibrolytic microbial consortium (MC/MCLp) promoted heterofermentative pathways, increasing acetic acid. These results highlight the potential of enzyme-bacterial synergy for improving fermentation quality of Elymus dahuricus.