Succession of Microbial Communities of Corn Silage Inoculated with Heterofermentative Lactic Acid Bacteria from Ensiling to Aerobic Exposure

To further explore the effects of heterofermentative lactic acid bacteria (LAB) on silage fermentation and aerobic stability, whole-plant corn at around the 1/2 milk-line stage was freshly chopped and ensiled in laboratory silos with deionized water (control), Lactobacillus buchneri (LB), or L. rhamnosus (LR). Each treatment was prepared in triplicate for 3, 14, and 60 d of fermentation, followed by 3 and 7 days of aerobic exposure. The dynamic changes in microbial community were studied by single molecule real-time (SMRT) sequencing. The results showed that the two LAB inoculants altered the microbial communities in different ways. Succession from L. plantarum to L. buchneri and L. rhamnosus was observed in LB- and LR-treated silage, respectively. Both silages improved aerobic stability (82 and 78 h vs. 44 h) by occupying the microbial niche to produce higher levels of acetic acid at terminal fermentation. Because Acetobacter fabarum dominated in the silages after aerobic exposure, beta diversity dramatically decreased. In this study, a. fabarum was reported for the first time in silage and was related to aerobic spoilage. The two heterofermentative LAB produced acetic acid and improved the aerobic stability of the corn silage by occupying the microbial niche at terminal fermentation. Inoculated L. rhamnosus had a greater pH for a longer period of time after opening and less DM loss at day 7.