AUTHOR=Huang Rong Zheng , Wang Xuzhe , Ma Chunhui , Zhang Fanfan 

TITLE=Effects of intrinsic tannins on proteolysis dynamics, protease activity, and metabolome during sainfoin ensiling

JOURNAL=Frontiers in Microbiology

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.976118

DOI=10.3389/fmicb.2022.976118

ISSN=1664-302X

ABSTRACT=CT from sainfoin have strong ability to inhibit proteolysis. Previous study observed that CT of sainfoin inhibit lactic acid bacteria activity and decreased ammonia content during sainfoin ensiling, but none of them focus on metabolic in sainfoin ensiled. The objective of this study was to investigated the effects of CT (through addition with polyethylene glycol (PEG) to deactivated CT) on protease activities, keystone bacteria and metabolome during sainfoin ensiling. The results showed that addition with PEG increased non-protein nitrogen, amino acid and soluble protein content during ensiling (increased proportion rang from 49.08%-59.41%, 116.01%-164.22%, 23.5%-41.94%, respectively, p< 0.05), decreased neutral detergent -insoluble protein and acid detergent -insoluble protein during ensiling (decreased proportion rang from 55.98%-64.71% and 36.58%-57.55%, respectively, p< 0.05). Addition with PEG increased aminopeptidase and acid protease activity after 3 d of ensiling (p< 0.05), increased carboxypeptidase activity during entire ensiling process (p< 0.05). The keystone bacteria shifted by addition with PEG (Stenotrophomonas, Pantoea and Cellulosimicrobium in control vs. Microbacterium, Enterococcus, and Brevundimonas in PEG treated group). The total 510 metabolites were identified after 60 d of sainfoin ensiling, which 33 metabolites were annotated to KEGG data base. Among those metabolites, phospholipids were the most abundant (72.7% of total 33 metabolites). 10 up-regulated metabolites and 23 down-regulated metabolites were identified in the PEG treated group compare with control after 60 d of ensiling (p< 0.05). The Pediococcus (correlated with 20 metabolites, R> 0.88, p< 0.05) and Lactobacillus (correlated with 16 metabolites, R> 0.88, p< 0.05) were most bacteria correlated with metabolites. The results suggested that there might had antagonistic effects between Lactobacillus and Pediococcus during ensiling. The proteolysis decreased during sainfoin ensiling mainly attributed to protease activity inhibit by CT, particularly for carboxypeptidase activity. In addition, proteolysis decreased partly attributed to CT inhibit Pediococcus activity during ensiled results from Pediococcus had significant highly positive correlated with dopamine after 60 d of ensiling (R=0.8857, p< 0.05).