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Effects on microbial diversity of fermentation temperature (10°C and 20°C), long-term storage at 5°C, and subsequent warming of corn silage

ABSTRACT: Objective:To evaluate the effects on microbial diversity and biochemical parameters of gradually increasing temperatures, from 5 to 25 °C on corn silage which was previously fermented at ambient or low temperature. Methods:Whole-plant corn silage was fermented in vacuum bag mini-silos at either 10 or 20 °C for two months and stored at 5 °C for two months. The mini-silos were then subjected to additional incubation from 5 to 25 °C in 5 °C increments. Bacterial and fungal diversity was assessed by PCR-DGGE profiling and biochemical analysis from mini-silos collected at each temperature. Results:A temperature of 10 °C during fermentation restricted silage fermentation compared to fermentation temperature of 20 °C. As storage temperature increased from 5 to 25 °C, little changes occurred in silages fermented at 20 °C, in terms of most biochemical parameters as well as bacterial and fungal populations. However, a fairly high number of enterobacteria and yeasts (4-5 log10 CFU g FM-1) were detected at 15 °C and above. PCR-DGGE profile showed that Candida humilis predominated the fungi flora. For silage fermented at 10 °C, no significant changes were observed in most silage characteristics when temperature was increased from 5 to 20 °C. However, above 20 °C, silage fermentation resumed as observed from the significantly increased number of LAB colonies, acetic acid content, and the rapid decline in pH and WSC concentration. DGGE results showed that Lactobacillus buchneri started to dominate the bacterial flora as temperature increased from 20 to 25 °C. Conclusion:Temperature during fermentation as well as temperature during storage modulates microorganism population development and fermentation patterns. Silage fermented at 20 °C indicated that these silages should have lower aerobic stability at opening because of better survival of yeasts and enterobacteria.

SUBMITTER: Zhou Y

PROVIDER: S-EPMC6718904 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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Project description:The objective of this study was to investigate effects of different lactic acid bacteria (LAB) on the fermentation process of whole-plant corn silage stored at different temperatures based on bacterial community successions, interaction networks, and predicted functions. Before ensiling, whole-plant corn was inoculated with L. plantarum (LP) or L. buchneri (LB) and the silage bags were stored at 20 or 30°C, and sampled after 0.5, 1, 3, 7, 14, and 60 d of ensiling. The higher abundances of Leuconostoc, Pedicoccus and Weissella were observed in silage stored at 30°C after 12 h of ensiling, thereby rapidly decreased pH to about 4.5. According to meta-network analysis, the bacterial communities were more sensitive to storage temperature than LAB inoculants during whole-plant corn ensiling. Species of Lactobacillus and Weissella were sensitive to 30°C, while Leuconostoc species were sensitive to 20°C in whole-plant corn silage. The storage temperature of 30°C decreased bacterial diversity and network complexity of whole-plant corn silage compared with 20°C. Additionally, LP inoculation changed the bacterial community successions during the early and middle ensiling periods, while LB inoculation affected bacterial community successions in the later stage of ensiling. The metabolic pathways of bacterial community were totally different in LB-inoculated silage from that in control and LP-inoculated silage. As the bacterial compositions became simple along with the ensiling process, the functional structure of bacterial community became simplified as well. In general, the storage temperature had a greater impact on the fermentation characteristics, bacterial community and predicted function of whole-plant corn silage compared with LAB inoculations. IMPORTANCE Increased understanding of effects of regulation measures on whole-plant corn silage is important from bacterial community succession, interaction network and predicted functions. According to alpha diversity and meta co-occurrence network, the bacterial communities were more sensitive to storage temperature than LAB inoculants during whole-plant corn ensiling. The storage temperature of 30°C decreased bacterial diversity and network complexity of whole-plant corn silage compared with 20°C. In addition, 30°C promoted the initiation of LP and LB inoculants, and 20°C was conducive to the long-term growth of LP and LB inoculants. According to the changes of bacterial community and predicated functions, it was further confirmed that the effect of LB inoculation was more obvious on whole-plant corn silage.

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Effects on microbial diversity of fermentation temperature (10°C and 20°C), long-term storage at 5°C, and subsequent warming of corn silage

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