# Microbial Community and Functional Analysis of Regionally Produced Traditional Korean Grain Vinegar
## 1 Introduction  
Vinegar is a fermented food widely consumed around the world, with a tradition that dates back to ancient times [1]. Due to its unique taste, aroma, and beneficial health effects, vinegar has long been used as a commitment and preservative. In countries such as Korea, Japan, China, and Spain, traditional vinegar production methods involve fermenting grain- or fruit-based raw materials [2]. Various types of vinegar exist depending on the country or region. The flavor, aroma, and health benefits of vinegar are largely determined by the microbial composition, raw materials, and technical methods used in the fermentation process [3, 4, 5].  
The traditional vinegar fermentation process is divided into two stages. The first stage, alcohol fermentation, is the process by which yeast converts sugars into alcohol. The second stage, acetic acid fermentation, is the process through which acetic acid bacteria convert this alcohol into acetic acid [6]. Thus, vinegar fermentation is driven by a range of microorganisms that affect the product's final quality. Previous studies have shown that identifying changes in microbial communities during vinegar fermentation can provideimportant clues for improving vinegar quality or discovering new health benefits [7; 8; 9]. Microbial community analyses have been conducted on various fermentation systems, ranging from traditional to modern, advanced methods. These analyses have helped identify key microorganisms involved in vinegar fermentation, thereby improving fermentation efficiency [4; 10].  
Traditional fermented vinegars in Korea, which undergo natural fermentation processes, are mainly grain vinegars made from rice and barley and fruit vinegars made from apples and pears. However, with the advancement of brewing techniques for grain-based liquors, a food culture centered around grain vinegar has emerged [11; 12]. Since the 1990s, there has been an increased awareness of health promotion and dietary habits, leading to the growing popularity of traditional vinegars, which are considered to have superior functional properties compared to commercial vinegars [13]. In natural fermentation processes, which do not involve starter cultures, flavors and functional components are generated by the activities of undefined microbial communities. Therefore, it is necessary to identify these microorganisms [14; 15].  
Therefore, in this study, traditional Korean grain vinegars were collected from different regions, and the changes in microbial communities and the correlations of functional components over the course of fermentation were monitored. Based on this data, we aimed to identify the dominant microorganisms as well as the growth of harmful microorganisms during the fermentation process and understand the impact of raw materials and environmental factors on microbial growth. The results of this study are expected to provide foundational insights into the relationships between raw materials, microbial communities, and functional compounds in traditional grain vinegars. These findings may guide the optimization of fermentation conditions, the standardization of production processes, and the development of high-quality, health-promoting vinegars, thereby contributing to the sustainable growth of the vinegar industry.