## 3 Results  
### Active Microbial Community Diversity and Composition  
Taxonomic annotation of the active microbial community at the superkingdom level indicated that the relative abundance of bacteria and fungi was 40.83% and 40.31%, respectively, at the beginning of fermentation. The relative abundance of bacteria gradually increased to 46.23%, and that of fungi decreased to 25.30% on the 16 th day of fermentation. Subsequently, the relative abundance of bacteria and fungi reached 45.40% and 29.55% at the end of fermentation, respectively. In addition to the bacteria and fungi, the relative abundance of archaea and viruses accounted for 0.0036-0.0068% and 0.056-0.15%, respectively, during the fermentation (Figure S2). According to the microbial abundance analysis, the active microbial community with relative abundances higher than 0.1% or 1% at the genus and species level were picked and analyzed (Table S1). When the relative abundance higher than 0.1% was selected, there were 39 genera and 59 species in at least one sample at the beginning of fermentation, then the numbers gradually decreased, and only 21 genera and 37 species existed until the 8 th day of fermentation. There were 26 genera and 45 species when the fermentation finished. When a relative abundance higher than 1% was selected, a total of 14 genera and 19 species in at least one sample at the beginning of fermentation, then the numbers dropped to 9 genera and 12 species at day 6 of fermentation and remained stable until the end of fermentation. These results indicated that the diversity of the microbial community decreased along with the fermentation process.  
A previous study reported that a total of 421 genera were annotated during NLS fermentation by metatranscriptomic analysis [11]. In this study, the microbial community at the genus and species level with a relative abundance higher than 1%, which included 19 genera and 28 species, was comprehensively analyzed. At the beginning of fermentation, the fungal genera, including _Saccharomyces_, _Talaronyces_, and _Aspergillus_, and the bacterial genera, including _Lactobacillus_, _Pediococcus_, _Streptococcus_, and _Campylobacter_, constituted the active predominant genera. Then, the relative abundances of _Streptococcus_, _Saccharomyces_, _Clavispora_, and _Colletotrichum_ were further increased and accompanied by a sharp decline in _Aspergillus_, _Pediococcus_, and _Campylobacter_ at days 6 and 8 of fermentation. In addition to thegenera of _Saccharomyces_, _Talaromyces_, _Lactobacillus_, and _Streptococcus_, which were the active predominant genera, there was a dramatic increase in _Faecalibacterium_ and _Thermotoga_ at the end of fermentation (Figure 1A).  
There were 885 species annotated during NLS fermentation using metatranscriptomic analysis. Species _S. cerevisiae_, _L. oakiensis_, _T. marneffei_, _L. heleticius_, _P. dammosus_, and _A. niger_ were dominant at the beginning of fermentation. As the fermentation progresses, the relative abundance of _S. mutans_, _L. brevis_, _L. pasteurii_, _Lactobacillus_ sp. ASF360 and _C. lusitaniae_ increased sharply, and the abundance of _L. oakiensis_, _T. marneffei_, _L. heleticius_, _P. dammosus_, and _A. niger_ decreased simultaneously on day 8 of fermentation. The late stage of fermentation was characterized by the dramatic increase in _F. prasuntizii_, _Thermotoga_ sp. TBYP3.1.4.1 and _L. acettolerans_. When the fermentation proceeded to the late stage, the increase in acids and alcohol inhibited the growth of other _Lactobacillus_ with weak acid and  
Figure 1: Taxonomic annotation of the active microbial community during NLS fermentation. (**A**) Distribution of the active microbial community with a relative abundance higher than 1% at the genus level. (**B**) Distribution of the active microbial community with a relative abundance higher than 1% at the species level.  
alcohol tolerance, resulting in the accumulation of _L. acettolerans_ (Figure 1B). Our results indicated that the active microbiota displayed a dynamic change in NLS fermentation.