Table_2_Microbiomics and volatile metabolomics-based investigation of changes in quality and flavor of oat (Avena sativa L.) silage at different stages.xlsx

ObjectiveThis study aimed to analyze the fermentation quality, microbial community, and volatile metabolites of oat silage harvested at two different stages, while examining the correlation between microorganisms and volatile metabolites.
MethodsOats were harvested at two growth stages (pre-heading [PRH] and post-heading [POH] stages), followed by 90 days of natural fermentation, with 6 replicates per treatment. Pre- and post-silage samples were randomly selected for nutrient composition, fermentation parameters, microbial population, and high-throughput sequencing analysis. Volatile metabolomics analysis was also performed on samples after 90 days of fermentation to detect differences in flavor quality after silage.
ResultsThe effect of growth stage on the nutrient content of oats was significant, with pre-heading oats having higher crude protein and post-heading oats having higher water soluble carbohydrates content (p < 0.05). Following a 90-day fermentation period, the pH and ammonia nitrogen/total nitrogen levels in the PRH-90 (silage from pre-heading oats after 90 days of fermentation) group demonstrated a significant decrease (p < 0.05), whereas the lactic acid content was notably higher compared to the POH-90 (silage from post-heading oats after 90 days of fermentation) group (p <0.05). Lactiplantibacillus dominated in the PRH-90 group and Enterococcus dominated in the POH-90 group, with abundances of (> 86%) and (> 87%), respectively. The differential volatile metabolites of the two treatment groups were dominated by esters and terpenoids, and the differences in flavor were mainly concentrated in sweet, green, and fruity odors. The results of Kyoto encyclopedia of genes and genomes pathway enrichment analysis demonstrated three major metabolic pathways: phenylpropanoid biosynthesis, phenylalanine metabolism, and biosynthesis of secondary metabolites. Specific microorganisms were significantly correlated with flavor indicators and flavor metabolites. Lactiplantibacillus was significantly positively correlated with flavor substances indicating sweet and fruity flavors, contributing to good flavor, while Enterococcus was significantly and positively correlated with flavor substances indicating bad flavors.
ConclusionIn summary, growth stage had significant effects on nutritional components, fermentation parameters and flavor quality of oats, with the fermentation process dominated by Lactiplantibacillus leading to good flavor, while the fermentation process dominated by Enterococcus led to the development of poor flavor.

### 研究目的
本研究旨在分析两个不同收获期燕麦青贮（oat silage）的发酵品质、微生物群落与挥发性代谢产物，并探究微生物与挥发性代谢产物之间的相关性。
### 试验方法
试验于两个生长阶段（抽穗前期[pre-heading, PRH]与抽穗后期[post-heading, POH]）收获燕麦，随后进行90天自然发酵，每个处理设置6次生物学重复。分别在青贮制备前后随机取样，开展营养成分、发酵参数、微生物菌群及高通量测序（high-throughput sequencing）分析；发酵90天后的样品同步开展挥发性代谢组学（volatile metabolomics）分析，以检测青贮后风味品质的差异。
### 试验结果
生长阶段对燕麦营养成分具有显著影响，抽穗前期燕麦的粗蛋白含量更高，而抽穗后期燕麦的水溶性碳水化合物含量更优（p < 0.05）。经过90天发酵后，PRH-90组（抽穗前期燕麦发酵90天的青贮样品）的pH值与氨氮/总氮水平均显著降低（p < 0.05），而乳酸含量显著高于POH-90组（抽穗后期燕麦发酵90天的青贮样品）（p < 0.05）。PRH-90组的优势菌属为植物乳杆菌属（Lactiplantibacillus），丰度占比>86%；POH-90组的优势菌属为肠球菌属（Enterococcus），丰度占比>87%。两组样品的差异挥发性代谢产物以酯类与萜类化合物为主，风味差异主要集中在甜香、青草香与果香气味。京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes, KEGG）通路富集分析结果显示，共富集到3条主要代谢通路：苯丙烷生物合成、苯丙氨酸代谢以及次级代谢产物生物合成。特定微生物类群与风味指标及风味代谢产物呈显著相关性：植物乳杆菌属与表征甜香、果香的风味物质呈显著正相关，有助于形成优良风味；而肠球菌属与表征不良风味的风味物质呈显著正相关。
### 研究结论
综上，生长阶段对燕麦的营养成分、发酵参数及风味品质均具有显著影响；以植物乳杆菌属为主导的发酵过程可形成优良风味，而以肠球菌属为主导的发酵过程则会导致风味品质劣变。