Influences of Bacillus coagulans on microbial community and fermentation profile of alfalfa silage compare with conventional lactic acid bacteria strains

AbstractsAlfalfa (Medicago sativa L.) silage is often difficult to preserve due to low soluble sugar and high buffering capacity, which can promote undesirable microorganism growth. Adding lactic acid bacteria (LAB) is commonly used to improve fermentation. Bacillus coagulans is a facultative anaerobe capable of producing lactic acid, but its application in alfalfa silage has rarely been reported. This study evaluated the effects of B. coagulans on bacterial community and fermentation quality of alfalfa silage, comparing it with two conventional LAB strains (Lactobacillus plantarum and Pediococcus acidilactici). First-cut early flowering alfalfa was wilted, chopped, and inoculated with B. coagulans (Group B), L. plantarum (Group L), P. acidilactici (Group P), or sterile water as control (Group CK). After 45 days of ensiling at room temperature, samples were analyzed for nutritional composition, fermentation parameters, and bacterial community via 16S rRNA sequencing. B. coagulans inoculation did not significantly affect nutritional composition (CP, NDF, ADF, Lignin, NDFD30, TDN, and NFC) compared to conventional LAB treatments (p > 0.05), but it resulted in higher pH and ammonia nitrogen (NH3-N) levels (p < 0.05). Bacterial diversity (Chao1, ACE, Shannon, Simpson indices) was significantly higher in Group B than in Group L and P (p < 0.05), similar to the Group CK. At the phylum level, Group B showed lower Firmicutes and higher Proteobacteria abundance. PCoA-envfit analysis revealed that Group B clustered with Group CK, separate from Group L and P, with VFA, NH3-N, AA, pH, and LA identified as key factors shaping community structure (p < 0.1). In conclusion, B. coagulans was less effective than traditional LAB in improving alfalfa silage fermentation. Its weak inhibitory effect on microbial communities led to higher bacterial diversity and slower reduction of pH. Thus, B. coagulans is not recommended as a sole inoculant for alfalfa silage under the tested conditions.