Abstract
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.
Highlights
During silage fermentation, epiphytic lactic acid bacteria (LAB) consume sugars under anaerobic conditions to produce lactic and acetic acid, which lower the pH of the silage, thereby inhibiting the harmful effects of enterobacteria, clostridium, yeast, and mold.According to the varieties of LAB, there are different types of fermentation
There was no significant difference in the acetic acid concentrations between the Lactobacillus buchneri (LB) and L. rhamnosus (LR) treatments at 60 d of ensiling and 3 d of aerobic exposure (p > 0.05); both were in the range of 2.5–3.3% Dry matter (DM), while LR-treated silage had significantly higher acetic acid levels than LB-treated silage at 7 d of aerobic exposure (p < 0.05)
Our study study found found that that the the number number of of stability yeasts, molds, and enterobacteria increased by prolonging the aerobic exposure time, and yeasts, molds, and enterobacteria increased by prolonging the aerobic exposure time, and heterofermentative LAB
Summary
Epiphytic lactic acid bacteria (LAB) consume sugars under anaerobic conditions to produce lactic and acetic acid, which lower the pH of the silage, thereby inhibiting the harmful effects of enterobacteria, clostridium, yeast, and mold. Li and Nishino [19] observed similar results in Italian ryegrass silage These two LAB inoculants produced few changes in bacterial and fungal communities in corn silage [20]. These inconsistent results may be due to the different forage types and strains used. We hypothesized that L. buchneri and L. rhamnosus could improve the fermentation profile and aerobic stability by affecting dynamic changes in the microbial communities of corn silages in different ways. The object of this study was to investigate the dynamic changes of corn silage microbial communities and fermentation profiles via SMRT technology inoculated with the commercial inoculant L. buchneri and the screened strain L. rhamnosus
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