Using γ-ray irradiation and epiphytic microbiota inoculation to separate the effects of chemical and microbial factors on fermentation quality and bacterial community of ensiled Pennisetum giganteum

Abstract

Aims: This study aimed to separate the effects of chemical and microbial factors on the fermentation quality and bacterial community of ensiled Pennisetum giganteum. Methods and Results: Fresh P. giganteum of two vegetative stages (stage I, G I ; stage II, G II ) was treated as follows: G I epiphytic microbiota + γray presterilized G I (M I C I ), G II epiphytic microbiota + γray presterilized G I (M II C I ), G I epiphytic microbiota + γray presterilized G II (M I C II ), and G II epiphytic microbiota + γray presterilized G II (M II C II ). Triplicates per treatment were sampled after 30 days of ensiling for chemical and microbial analyses and high-throughput sequencing. Silages made from C II (M I C II and M II C II ) had higher lactic acid concentration and the ratio of lactic to acetic acid, and lower pH and ammonia nitrogen concentration than silages produced by C I (M I C I and M II C I ). Species differential analyses showed that the changes of chemical composition rather than epiphytic microbiota significantly affected the relative abundance of Lactobacillus, Pediococcus and Pantoea in P. giganteum silages. Conclusion:These above results manifested that chemical composition was the main factor influencing the fermentation quality and bacterial community of P. giganteum silage in this study. Significance and Impact of the Study:The obtained results may, therefore, be the first record to provide an in-depth understanding of the relative contributions of chemical and microbial parameters on fermentation quality and bacterial community, which is of great importance for modulating silage fermentation and improving silage quality.

Separating the chemical and microbial factors of oat harvested at two growth stages to determine the main factor on silage fermentation

“…Gamma‐ray irradiation at 32 kGy can successfully sterilize oat without destroying the chemical integrity, which was consistent with our previous works (Wang et al, 2020; Zhao, Yin, Dong, et al, 2021). Gamma‐ray irradiation is a potential technology to separate the effects of micro‐organisms on various environments.…”

“…The result of Zhao et al (2021) showed that due to the effect of chemical component of fresh forage, the epiphytic microbiota could not forecast the outcome of silage fermentation. In the present work, similar results were found that although the epiphytic microbiota in the two growth stages was different, the difference in epiphytic microbiota did not significantly influence the fermentation of oat.…”

Changes in the fermentation products, taxonomic and functional profiles of microbiota during high-moisture sweet sorghum silage fermentation

“…Unsurprisingly, the number of aerobic bacteria and molds that cannot tolerate anaerobic conditions continuously decreased to a negligible or undetectable level as ensiling proceeded and O 2 depleted. And the negligible or undetected number of yeast and enterobacteria in SSS was associated with the low pH value ( Zhao et al, 2022 ). Considering that yeast is more resistant to acid, the decrease of yeasts in SSS was also related to the rapid proliferation of LAB as the former are less competitive under anaerobic and acidic conditions ( McDonald et al, 1991 ; Zhao et al, 2021 ).…”

“…Thus, SS, 7-day SSS (SSS-7), and 60-day SSS (SSS-60) were sampled for the analyses of bacterial diversity and potential function. The bacterial DNA extraction and polymerase chain reaction (PCR) amplification were conducted according to the procedures reported in our previous study ( Zhao et al, 2022 ). The purified amplicons were paired-end sequenced on the Illumina MiSeq PE300 platform (Illumina Inc., San Diego, CA, United States).…”

The effects of epiphytic microbiota and chemical composition of Italian ryegrass harvested at different growth stages on silage fermentation

“…Ensiling is a common forage preservation method that relies on lactic acid bacteria fermentation to convert accessible chemical composition of fresh forage into organic acids, reduce pH and restrict the activities of undesirable microbes. 2,3 The fermentation quality and nutritional value of silage depend largely on the growth stage of forage at harvest 4 because the accessible chemical composition of lactic acid bacteria can vary from the growth stage of forage, such as dry matter (DM), 5 buffering capacity (BC) 6 and water-soluble carbohydrates (WSC). 7 Besides the chemical composition, the growth stage of forage could also influence the epiphytic microbiota, which starts spontaneous fermentation as long as the anaerobic environment is formed.…”