Screening of low-temperature fermentation lactic acid bacteria from silage of Elymus nutans growing on the Qinghai-Tibetan Plateau

Abstract:

[Objective] This study is aimed to investigate lactic acid bacteria diversity in Elymus nutans silage, and selected out lactic acid bacteria which grew well at low temperatures of 10, 15 and 25 °C. [Methods] Lactic acid bacteria (LAB) strains isolated from Elymus nutans silages were identified by 16S rRNA gene sequences. Meanwhile MRS medium was used to choose high absorbance LAB from each species at different temperatures (10, 15 and 25 °C), and green juice fermentation was used to get the low PH value one as the dominant LAB at different temperatures (10, 15 and 25 °C). [Results] A total of 108 LAB strains were isolated from a variety of stages of fermentation at different temperatures. Based on 16S rRNA gene sequence analysis and phylogenetic tree, these 108 strains were classified into 6 genera and 18 species. In combination with the screening results of culture medium and fermented green juice, we found that LS-24 showed obvious growth advantage at 15 °C (P<0.05), and PP-63 grew faster in the early stage of fermentation, while LP-21 made pH value dropped to 3.9 at 15 °C and had the maximum number of viable cellseory. [Conclusion] The lactic acid bacteria found in this experiment covered almost all common lactic acid bacteria genera found in silages, but species were fewer as compared to the reported lactic acid bacteria from silages. LP-21, LS-24 and PP-63 show a good growth and fermentation characteristics, therefore, these three strains were selected as preferred candidates of lactic acid bacteria strains for low temperature fermentation of ensiling forage.