Effects of storage time on the fermentation quality， bacterial community composition， and functional profile of sweet sorghum silage

doi:10.11686/cyxb2022384

Abstract

Abstract:

In this study， we aimed to evaluate the chemical composition， fermentation quality， microbial community， and functional shifts of sweet sorghum （SS） during ensiling. SS harvested at the hard dough stage was naturally ensiled for 1， 3， 7， 15， 30， and 60 days. After opening the silo， SS silage （SSS） was randomly sampled for analyses of chemical composition， fermentation parameters， and microbial abundance. Fresh， 7-day， and 60-day SSS were further subjected to high-throughput sequencing and Kyoto Encyclopedia of Genes and Genomes （KEGG） functional prediction analyses. After 60 days of ensiling， SSS displayed homolactic fermentation as characterized by a lack of butyric acid， a low pH value， a high lactic acid concentration， and a high ratio of lactic to acetic acid. Enterobacter （26.0%） and Pantoea （25.7%） were the most common genera in fresh SS， while Leuconostoc （34.1%） and Lactococcus （31.6%） were dominant in 7-day SSS and were subsequently replaced by Lactobacillus （73.5%） in 60-day SSS. A heatmap constructed using Spearman’s correlation coefficient values showed that Lactobacillus was positively related to the lactic acid concentration and negatively related to the pH value. The KEGG metabolic profiles differed substantially between before and after ensiling. The ensiling process downregulated the metabolism of amino acids， energy， cofactors and vitamins， but upregulated the metabolism of nucleotides and carbohydrates. Overall， high-throughput sequencing combined with KEGG functional prediction analyses further confirmed the succession of cocci-shaped lactic acid bacteria to rod-shaped lactic acid bacteria during the SS ensilage process， and revealed trends of up-regulated carbohydrate metabolism and down-regulated amino acid metabolism. A thorough knowledge of the changes in bacterial community dynamics and functional shifts of SS during ensiling is important for understanding the fermentation mechanism and may contribute to the production of high-quality SSS.

Key words: sweet sorghum, fermentation quality, microbial community succession, functional shifts, silage

Jie ZHAO, Xue-jing YIN, Si-ran WANG, Zhi-hao DONG, Jun-feng LI, Yu-shan JIA, Tao SHAO. Effects of storage time on the fermentation quality， bacterial community composition， and functional profile of sweet sorghum silage[J]. Acta Prataculturae Sinica, 2023, 32(8): 164-175.

Figures/Tables 9

References 36

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项目Item	含量Content
pH	5.23±0.04
干物质Dry matter （%鲜重Fresh weight）	31.90±1.08
水溶性碳水化合物Water-soluble carbohydrates （%DM）	28.40±0.41
粗蛋白Crude protein （%DM）	5.13±0.61
缓冲能Buffering capacity （mEq·kg^-1 DM）	50.90±6.05
中性洗涤纤维Neutral detergent fiber （%DM）	55.30±0.29
酸性洗涤纤维Acid detergent fiber （%DM）	29.50±0.15
乳酸菌Lactic acid bacteria （lg CFU·g^-1 FW）	8.59±0.06
好氧性细菌Aerobic bacteria （lg CFU·g^-1 FW）	8.57±0.04
酵母菌Yeasts （lg CFU·g^-1 FW）	7.86±0.03
霉菌Molds （lg CFU·g^-1 FW）	6.00±0.14
肠杆菌Enterobacteria （lg CFU·g^-1 FW）	8.67±0.10

项目Item	含量Content
pH	5.23±0.04
干物质Dry matter （%鲜重Fresh weight）	31.90±1.08
水溶性碳水化合物Water-soluble carbohydrates （%DM）	28.40±0.41
粗蛋白Crude protein （%DM）	5.13±0.61
缓冲能Buffering capacity （mEq·kg^-1 DM）	50.90±6.05
中性洗涤纤维Neutral detergent fiber （%DM）	55.30±0.29
酸性洗涤纤维Acid detergent fiber （%DM）	29.50±0.15
乳酸菌Lactic acid bacteria （lg CFU·g^-1 FW）	8.59±0.06
好氧性细菌Aerobic bacteria （lg CFU·g^-1 FW）	8.57±0.04
酵母菌Yeasts （lg CFU·g^-1 FW）	7.86±0.03
霉菌Molds （lg CFU·g^-1 FW）	6.00±0.14
肠杆菌Enterobacteria （lg CFU·g^-1 FW）	8.67±0.10

项目 Item	贮藏时间Ensiling time （d）						SEM	P值 P-value
项目 Item	1	3	7	15	30	60	SEM	P值 P-value
pH	4.47A	3.95B	3.76C	3.70CD	3.61D	3.59D	0.072	<0.001
乳酸Lactic acid （LA， %DM）	0.64A	4.29A	5.80A	7.85A	12.40A	13.20A	1.887	0.438
乙酸Acetic acid （AA， %DM）	0.15C	0.78BC	1.13BC	1.90ABC	2.34AB	3.19A	0.276	0.002
乳乙比LA/AA	4.45A	5.76A	5.43A	4.13A	3.17A	4.13A	0.449	0.518
丙酸Propionic acid （%DM）	0.04BC	0.02BC	0.00C	0.03BC	0.06B	0.11A	0.009	<0.001
正丁酸n-butyric acid （n-BA， %DM）	ND	ND	ND	ND	ND	ND	-	-
异丁酸Isobutyric acid （IBA， %DM）	ND	ND	ND	ND	ND	ND	-	-
挥发性脂肪酸Volatile fatty acid （VFA， %DM）	0.19C	0.79BC	1.14BC	1.93ABC	2.40AB	3.30A	0.173	0.002
乙醇Ethanol （%DM）	0.09B	0.04B	0.08B	0.16AB	0.23AB	0.33A	0.027	0.002
1，2-丙二醇1，2-propanediol （%DM）	ND	ND	ND	ND	ND	ND	-	-
干物质Dry matter （%FW）	32.3A	31.1AB	29.6B	29.5B	29.1B	29.5B	0.315	0.006
水溶性碳水化合物WSC （%DM）	28.2A	25.1A	25.2A	19.2B	18.2BC	14.4C	1.174	<0.001
氨态氮Ammonia nitrogen （NH₃-N， %TN）	6.48A	7.68A	7.75A	7.68A	8.01A	8.51A	0.230	0.245

项目 Item	贮藏时间Ensiling time （d）						SEM	P值 P-value
项目 Item	1	3	7	15	30	60	SEM	P值 P-value
pH	4.47A	3.95B	3.76C	3.70CD	3.61D	3.59D	0.072	<0.001
乳酸Lactic acid （LA， %DM）	0.64A	4.29A	5.80A	7.85A	12.40A	13.20A	1.887	0.438
乙酸Acetic acid （AA， %DM）	0.15C	0.78BC	1.13BC	1.90ABC	2.34AB	3.19A	0.276	0.002
乳乙比LA/AA	4.45A	5.76A	5.43A	4.13A	3.17A	4.13A	0.449	0.518
丙酸Propionic acid （%DM）	0.04BC	0.02BC	0.00C	0.03BC	0.06B	0.11A	0.009	<0.001
正丁酸n-butyric acid （n-BA， %DM）	ND	ND	ND	ND	ND	ND	-	-
异丁酸Isobutyric acid （IBA， %DM）	ND	ND	ND	ND	ND	ND	-	-
挥发性脂肪酸Volatile fatty acid （VFA， %DM）	0.19C	0.79BC	1.14BC	1.93ABC	2.40AB	3.30A	0.173	0.002
乙醇Ethanol （%DM）	0.09B	0.04B	0.08B	0.16AB	0.23AB	0.33A	0.027	0.002
1，2-丙二醇1，2-propanediol （%DM）	ND	ND	ND	ND	ND	ND	-	-
干物质Dry matter （%FW）	32.3A	31.1AB	29.6B	29.5B	29.1B	29.5B	0.315	0.006
水溶性碳水化合物WSC （%DM）	28.2A	25.1A	25.2A	19.2B	18.2BC	14.4C	1.174	<0.001
氨态氮Ammonia nitrogen （NH₃-N， %TN）	6.48A	7.68A	7.75A	7.68A	8.01A	8.51A	0.230	0.245

项目 Item	贮藏时间Ensiling time （d）						SEM	P值 P-value
项目 Item	1	3	7	15	30	60	SEM	P值 P-value
乳酸菌LAB	8.58AB	9.21A	9.16A	9.06A	9.47A	8.07B	0.128	0.003
好氧性细菌Aerobic bacteria	7.28A	5.22AB	3.54BC	3.38BC	2.09C	<2.00C	0.524	<0.001
酵母菌Yeasts	7.74	4.60	3.94	2.87	<2.00	ND	-	-
霉菌Molds	5.22	3.22	<2.00	ND	ND	ND	-	-
肠杆菌Enterobacteria	6.03	4.55	2.20	ND	ND	ND	-	-