Effect of isolated lactic acid bacteria on the quality and bacterial diversity of native grass silage

Objective

The objective of this study was to isolate lactic acid bacteria (LAB) from native grasses and naturally fermented silages, determine their identity, and assess their effects on silage quality and bacterial communities of the native grasses of three steppe types fermented for 60 days.

Methods

Among the 58 isolated LAB strains, Limosilactobacillus fermentum (BL1) and Latilactobacillus graminis (BL5) were identified using 16S rRNA sequences. Both strains showed normal growth at 15- 45°C temperature, 3-6.5% NaCl concentration, and pH 4-9. Two isolated LAB strains (labeled L1 and L5) and two commercial additives (Lactiplantibacillus plantarum and Lentilactobacillus buchneri; designated as LP and LB, respectively) were added individually to native grasses of three steppe types (meadow steppe, MS; typical steppe, TS; desert steppe, DS), and measured after 60 d of fermentation. The fresh material (FM) of different steppe types was treated with LAB (1 × 10⁵ colony forming units/g fresh weight) or distilled water (control treatment [CK]).

Results

Compared with CK, the LAB treatment showed favorable effects on all three steppe types, i.e., reduced pH and increased water-soluble carbohydrate content, by modulating the microbiota. The lowest pH was found in the L5 treatment of three steppe types, at the same time, the markedly (p < 0.05) elevated acetic acid (AA) concentration was detected in the L1 and LB treatment. The composition of bacterial community in native grass silage shifted from Pantoea agglomerans and Rosenbergiella nectarea to Lentilactobacillus buchneri at the species level. The abundance of Lentilactobacillus buchneri and Lactiplantibacillus plantarum increased significantly in L1, L5, LP, and LB treatments, respectively, compared with CK (p < 0.05).

Conclusion

In summary, the addition of LAB led to the shifted of microbiota and modified the quality of silage, and L. fermentum and L. graminis improved the performance of native grass silage.

Alternations of ensiling performance and bacterial community in response to different native grassland in Mongolian Plateau

AIMS

The aim of this study was to investigate the dynamics of bacterial communities and natural fermentation quality in three steppe types [meadow steppe (MS); typical steppe (TS); desert steppe (DS)] on the Mongolian Plateau.

METHODS AND RESULTS

PacBio single molecule with real-time sequencing technology (SMRT) was applied to provide insights into the dynamics of the physicochemical characteristics and the complex microbiome of native grass after 1, 7, 15, and 30 days of fermentation process. The dry matter, crude protein, and water soluble carbohydrate (WSC) contents of the three groups slowly decreased after 1 day of fermentation process, and the lowest WSC concentration after 30 day of ensiling was detected in the DS group compared to that in the MS and TS groups. There was no significant effect of steppe types on lactic acid and butyric acid content (P > 0.05). The pH was higher in the early stages of fermentation. After 30 days of fermentation, the pH of MS and DS dropped to about 5.60, while TS was as high as 5.94. At different ensiling days, the pH of TS was significantly higher than that of MS (P < 0.05). The ammonia nitrogen content of MS was significantly higher than TS and DS (P < 0.05). During the whole fermentation process, Leuconostoc mesenteroides and Pseudocitrobacter faecalis were the main species of DS, while Enterobacter roggenkampii and Faecalibacterium prausnitzii dominated the fermentation process in MS and TS, respectively.

CONCLUSIONS

The fermentation quality of native grass silage of different steppe types was less satisfactory, with the silage quality ranging from DS, MS and TS in descending order. The epiphytic bacteria dominating the fermentation process differed between steppe types of silage. Leuconostoc mesenteroides as the main strain of DS had a modulating effect on pH and LA content, while the main strains of MS and TS (Enterobacter roggenkampii and Faecalibacterium prausnitzii) dominated the silage without significant effect on improving fermentation characteristics and nutritional quality.