## 3 Results
### Correlations between the Active Microorganisms and the Volatile Flavors Based on O2 PLS-DA Model  
In order to investigate the correlation of the 14 genera with VIP > 1.0 and the top 20 volatile flavors, [PERSON]'s correlation analysis was performed, and their correlation was shown in Figure S6A. A total of 73 strong correlations (the absolute value of correlation coefficient \(\geq\) 0.8) were displayed. Among the 14 microorganisms with VIP > 1.0, the bacterial genus of _Streptococcus_ showed highly negative correlations with the production of 3-methylbutanoic acid, 3-methylbutanoic acid, 2-methylpropanoate, 3-methylbutanol and \(\beta\)-caryophyllene. On the contrary, the fungal genus of _Aspergillus_ was positively correlated with the production of 2-methylpropanoate, 3-methylbutanoic acid, 3-methylbutanol, \(\beta\)-caryophyllene, and negatively correlated with the production of ethanol and ethyl oleate. _Lactobacillus_ and _Rhizophagus_ were negatively correlated with the production of diethyl succinate and ethyl hydroxycaporate. Conversely, the fungal genus of _Talaroomyces_ was positively correlated with the production of ethyl hydroxycaporate and diethyl succinate. Other bacterial genera, including _Camyylobacter_, _Pediococcus_,  
Figure 6: O2 PLS-DA model based on the metatranscriptomics and metabolomics at the species level during NLS fermentation. (**A**) Top 20 species influencing the flavor compounds based on HS-SPME-GC-MS. (**B**) Top 20 compounds influencing the active species. (**C**) VIP plot of microbiota at the species level.  
Weissella, and _Yersinia_, and fungal genera, including _Gloeophyllum_ and _Mixia_, exhibited positive correlations with the production of 3-methylbutanoic acid, 2-methylpropanoate, 3-methylbutanol, 3-methylbutal and \(\beta\)-caryophyllene, and exhibited negative correlations with the production of ethanol, ethyl oleate, ethyl decanoate and ethyl linoleate (Figure 7A).  
The correlation between the 24 species with VIP \(>\) 1.0 and the top 20 volatile flavors was investigated based on [PERSON]'s correlation analysis, and their correlation was shown (Figure S6B). All 130 strong correlations (the absolute value of correlation coefficient \(\geq\) 0.8) were constructed, and 20 species were involved (Figure 7B). Among the 20 species, the bacterial species including _L. reuteri, L. heleticus, W. cibarta, P. pentosacteus, P. damosus, Yersinia pestis_ and _C. jejuni_, and fungal species including _G. rabeum_, S. stipites_ and _M. osmundae_ were positively correlated with the production of 3-methylbutanoic acid, 2-methylpropanoate, 3-methylbutanol, 3-methylbutal and \(\beta\)-caryophyllene, and were negatively correlated with the production of ethanol, ethyl oleate, ethyl decanoate and ethyl linoleate. In addition to exhibiting the above characteristics, _L. delbrueckii_ was also positively correlated with ether production. _K. marxianus, T. marneffefei, and _L. acetoleranus_ had a positive correlation with the production of diethyl succinate and ethyl-2-hydroxyaporate. However, _R. irregularis_ was negatively correlated with the above two compounds. _L. otakiensis_ was positively correlated with the production of 3-methylbutanol, 3-methylbutal and \(\beta\)-caryophyllene. The bacterial species, including _L. pasteurii_ and _S. mutans_, were negatively correlated with the production of 3-methylbutanoic acid, 2-methylpropanoate, 3-methylbutal, 3-methylbutal and \(\beta\)-caryophyllene, and \(L\). pasteurii was positively correlated with the ethanol production. The fungal species of _A. niger_ displayed the opposite pattern with _L. pasteurii_ for the production of 3-methylbutanoic acid, 2-methylpropanoate, 3-methylbutal, 3-caryophyllene and ethanol. Additionally, the bacterial species of _L. brevis_ exhibited a positive correlation with ethyl decanoate production.