# Microbial Community and Functional Analysis of Regionally Produced Traditional Korean Grain Vinegar
## 3 Results
### Microbial Community
tion process. However, _Kosakonia covanii_ was identified as an exception, as it is known to be an opportunistic pathogen associated with plant and human infections [27]. Therefore, its presence raises safety concerns and suggests the need for careful monitoring during vinegar production. Overall, _Lactobacillus acetotolerans_ was found to be the dominant species in the vinegars. _L. acetotolerans_ accounted for over 40% of the microbial community starting on day 0 of fermentation, indicating that it likely originated from the inoculated starter culture. Its early dominance suggests that it is well adapted to acidic conditions, which may have allowed it to outcompete other microbes. The starter was added at the beginning of fermentation, implying that the species was already present in high abundance within the starter culture. In the rice vinegar (JR), the microbial community established during the early stage of fermentation accounted for more than 90% throughout the fermentation process, peaking at 99.6% on day 10 (JR2). Similarly, the five-grain vinegar (YO) also showed a maximum occupancy of 98.2% on day 10 (YO2). _L. acetotolerans_ is known for its resistance to acidic environments such as alcohol and vinegar, and it is associated with increasing the acidity and improving the preservation of food. This finding aligns with previous studies wherein _L. acetotolerans_ was isolated from rice vinegar [28].  
The presence of _Acetobacter pasteurianus_ was notably high in the vinegar samples. In the brown rice vinegar (HB), _A. pasteurianus_ showed a rapid increase from 0.1% upon inoculation (HB1) to 36.5% on day 10 (HB2) and remained at 35.5% on day 20 (HB3). In the barley vinegar (SB) and rice vinegar (JR), the levels of _A. pasteurianus_ increased to 9.8% and 7.6%, respectively, by day 20. These results are consistent with the acidity measurements, where HB showed a rapid increase in acidity on day 10, whereas SB and JR exhibited higher acidity on day 20. Furthermore, _Lacticaseibacillus paracasei_ was observed to decrease in presence from 37.5% on day 0 (HB1) to 6.5% on day 10 (HB2), and then this figure increased again to 13.6% on day 20 (HB3). _L. paracasei_ is a strain that thrives in acidic environments, such as in cheese and yogurt. Some strains of _L. paracasei_ have been reported to exhibit probiotic potential, including the production of metabolites that may contribute to gut health [29].  
At the beginning of fermentation, _Lentilactobacillus hilgardii_ in HB, _Latilactobacillus curvatus_ in SB, and _Limosilactobacillus fermentum_ in YO showed relatively high occupancy rates. These are all types of lactic acid bacteria that consume sugars to produce lactic acid and play a role in inhibiting the growth of pathogens, as reported in previous studies. Their presence in the fermentation mash suggests that these species play an active role during the acetic acid fermentation process [30; 31; 32]. By identifying the dominant microorganisms  
Figure 2: Microbial communities in grain vinegars produced via different fermentation processes across four regions and over three fermentation stages.  
in the manufacturing process, we aim to contribute to the development of more-efficient acetic acid fermentation strategies. Additionally, we aim to identify vinegas that harbor beneficial microorganisms and to explore their health-promoting potential.