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Microbial community and fermentation dynamics of corn silage prepared with heat-resistant lactic acid bacteria in hot environment.

H. Guan

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06-23-2020

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Abstract:

T48
Microbial community and fermentation dynamics of corn silage prepared with heat-resistant lactic acid bacteria in hot environment.
H. Guan*1, Y. Shuai1, Y. Yan1, Y. Cai1,2, X. Zhang1. 1Sichuan Agricultural University Chengdu, China, 2Japan International Research Center for Agricultural Science (JIRCAS) Tsukuba, Ibaraki, Japan.

Abstract With global warming, high temperatures become an important factor that influence silage fermentation process in the world, especially in the tropical and sub-tropical areas. To develop a silage fermentation technique to adapt to global climate changes, the microbial community and fermentation dynamics of corn silage prepared with a heat resistant lactic acid bacterium under different high temperature conditions were studied. Corn was ensiled in laboratory silo, with and without 2 selected strains Lactobacillus salivarius LS358 and L. rhamnosus LR753, 2 type strains L. salivarius ATCC 11741T and L. rhamnosus ATCC 7469T, and a commercial inoculant L. plantarum. Every treatment used 3 mini PVC silos (3 kg of fresh forage, density as 250 kg/m3) as replicates. The ensiling temperatures were designed at 30�C as control and at 45�C as high temperature, and the sampling took place after 0, 3, 7, 14 and 60 d of fermentation. During ensiling at 30�C, the dominant bacteria genera gradually changed from Pediococcus and Lactobacillus to Lactobacillus in silages. When silage stored at 45�C, bacterial community became more complex and fragmented after 7 d of ensiling. Pectobacterium, Brevundimonas, and Bosea spp. became prevalent at terminal fermentation. High temperature significantly caused a shift from a homofermentative to a heterofermentative type of LAB population in corn silage. Notably, the presence of Acetobacter was associated with silage fermentation at high temperature. The higher (P < 0.05) pH values and DM losses were observed in the silages stored at 45�C than those at 30�C, and the lower (P < 0.05) ratio of lactic acid/ acetic acid were found in silages inoculated with strains LS358 and LR753 at 30�C. Generally, exogenous heterofermentative L. rhamnosus 753 had potential ability to survive at 45�C during first 2 weeks of ensiling, reduced pH and produced more acetic acid content. Due to high temperature silage is an uncontrolled fermentation process, analysis of bacterial community of silage by next-generation sequencing (NGS) can be used for optimization of the ensiling process and heat resistant strain L. rhamnosus 753 show potential ability to improve silage fermentation in tropics and subtropics.

Keywords: bacteria community, high temperature, corn silage.

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