## 1 Introduction  
Vinegar is produced industrially following two main methods: a slow process involving a static surface and a fast submerged fermentation process, also known as acetic acid fermentation (AAF) [1]. Traditional vinegar is generally produced via static surface fermentation. This technique is relatively inexpensive, and the time required for complete fermentation is longer than that required for rapid fermentation. Traditional grain vinegar produced through static surface fermentation has various physiological functions, including blood sugar control, lipid metabolism control, weight loss, antibacterial, antioxidant, and anticancer activity due to its organic acid, polyphenol, and melanoidin content [2; 3]. The quality of vinegar varies greatly depending on the raw material, fermentation method, and manufacturing method used. The acetic acid content, organic acid composition, and free amino acid composition affect the taste and influence the quality of vinegar [4]. Acetic acid bacteria (AAB), particularly _Acetobacter_ spp., are commonly used in vinegar production. The Korean Ministry of Food and Drug Safety ([[https://www.foodsafetykorea.go.kr/](https://www.foodsafetykorea.go.kr/)]([https://www.foodsafetykorea.go.kr/](https://www.foodsafetykorea.go.kr/)), accessed on 24 March 2023) allows limited use of _Acetobacter__aectio_ and _Acetobacter__pasteurians_ only in vinegar production. AAB, obligate aerobes, oxidize alcohols _Acetobacter_ and _Gluconacetobacter_ spp., which can tolerate particularly high concentrations of acetic acid, are used as industrial vinegar producers [5]. A highly complex microbial community and metabolites are involved in traditional AAF; however, the correlation between them is still poorly understood [6]. Identification of species and characterization of dominant strains in static AAF are desirable for stabilizing and improving fermentation [7; 8; 9; 10]. Spontaneous fermentation is driven by a complex microbial community; however, the use of a selected starter has resulted in the simplification of the microbial community used in the fermentation process [11]. Recently, there has been a growing interest in controlled multiple fermentation using two or more selected starters. Interactions among AABs can affect microbial growth and metabolite production. It has been reported that mixed fermentation of yeast generated synergistic effects such as increased enzyme activity and reduced production of acetaldehyde compared to single fermentation and can contribute to management of wine fermentation by controlling undesirable or spoiled microorganisms [11]. In contrast, the number of studies on multiple AABs that interact with each other in a complex way is insufficient. The optimal temperature for traditional static AAF is approximately 30 \({}^{\circ}\)C, and a slight temperature increase of 2-3 \({}^{\circ}\)C results in significant reductions in both the rate and yield of AAF [12]. Therefore, setting the optimal conditions, including the fermentation temperature, for traditional grain vinegar production is a major task to increase the fermentation rate and yield [8]. In this study, optimal fermentation conditions were used for single and multiple AAF starters. In our previous study, we investigated the microbiome of Korean traditional grain vinegars using a culture-independent microbiological technique, and correlations between sensory characteristics and fermentation temperature were found [2]. Recent studies reported that the ecological aspects of the microbial community influence metabolic activity and, ultimately, the composition of the fermentation product [13; 14]. Fermentation of various foods and beverages, including traditional vinegar, is a complex phenomenon involving microbial consortia, showing the importance of studying the microorganisms in fermented products [15]. Beta diversity analysis was used to quantify the similarity or distance between the microbiome pairs.