Acetic acid bacteria (AAB) are major contributors to the production of fermented vinegar, offering various cultural, culinary, and health benefits. Although the residual unpasteurized AAB after vinegar production are not pathogens, these are necessary and require safety evaluations, including antibiotic resistance, before use as a starter. In this research, we investigated the antibiotic resistance profiles of 26 AAB strains, including various species of Komagataeibacter and Acetobacter, against 10 different antibiotics using the E-test method. All strains exhibited resistance to aztreonam and clindamycin. Komagataeibacter species demonstrated a 50% resistance rate to ciprofloxacin, analogous to Acetobacter species, but showed twice the resistance rates to chloramphenicol and erythromycin. Genomic analysis of K. saccharivorans CV1 identified intrinsic resistance mechanisms, such as multidrug efflux pumps, thereby enhancing our understanding of antibiotic resistance in acetic acid-producing bacteria. These findings enhance understanding of antibiotic resistance in AAB for food safety and new antimicrobial strategies, suggesting the need for standardized testing methods and molecular genetic study.

Acetic acid bacteria (AAB) are major contributors to the production of fermented vinegar, offering various cultural, culinary, and health benefits. Although the residual unpasteurized AAB after vinegar production are not pathogens, these are necessary the safety evaluations including antibiotic resistance for the use as starters. In this research, we investigated the antibiotics resistance profiles of 26 AAB strains, including various species of Komagataeibacter and Acetobacter, against ten different antibiotics using the E-test method. All strains exhibited resistance to aztreonam and clindamycin. Komagataeibacter species demonstrated a 50% resistance rate to ciprofloxacin, analogous to Acetobacter species, but showed twice the resistance rates to chloramphenicol and erythromycin. Genomic analysis of K. saccharivorans CV1 identified intrinsic resistance mechanisms, such as multidrug efflux pumps, thereby enhancing our understanding of antibiotic resistance in acetic acid-producing bacteria. These findings enhance understanding of antibiotic resistance in AAB for food safety and new antimicrobial strategies, suggesting the need for standardized testing methods and molecular genetic study.

This study investigated changes in microbial communities and functional components during the fermentation of traditional Korean grain vinegars collected from various regions as well as the correlations among these components. Microbial community analysis revealed that Lactobacillus acetotolerans was the dominant microorganism, while Acetobacter pasteurianus numbers gradually increased during fermentation, playing a key role in acetic acid production. L. acetotolerans, known to thrive in acidic environments, contributed to increasing the acidity of the vinegar and enhanced its preservative properties. The rise in the levels of organic acids, particularly acetic acid, was influenced by the activity of these microorganisms. Additionally, the production of free amino acids, such as alanine, was influenced by interactions between the fermentation medium and microbial communities, significantly contributing to the vinegar’s sweetness. Volatile flavor compounds exhibited considerable diversity due to changes in microbial communities driven by raw-material differences. In particular, five-grain vinegar (YO) tended to generate more complex and intense flavor compounds, with uniformly elevated levels of aldehydes, acids, and ketones. These findings suggest that raw-material selection and fermentation conditions significantly influence the flavor and functional properties of grain vinegars, providing valuable foundational data for improving vinegar production processes to enhance flavor and functionality.

Traditional fermented foods harbor diverse microbial resources and provide an important reservoir for fermentation applications. We compared selected fermentation-related metabolite profiles of yeast strains isolated from traditional Korean fermentation starters and fermented foods, including nuruk and makgeolli. A total of 63 Saccharomyces cerevisiae strains and 23 non-Saccharomyces strains were cultured in YPD medium for 24 h, and volatile compounds, organic acids, and free amino acid-related compounds were analyzed. Non-Saccharomyces strains generally showed higher levels of ester compounds, whereas S. cerevisiae strains exhibited relatively higher levels of alcohol compounds. In particular, Kluyveromyces marxianus KJ-L showed high levels of both ester and alcohol-related volatile compounds, suggesting its potential as a candidate strain for further aroma-related evaluation. Organic acid and free amino-related profiles also differed between the two yeast groups. These results highlight the distinct metabolic traits of S. cerevisiae and non-Saccharomyces strains and provide useful screening information for selecting candidate microbial resources for further validation in fermented food systems.

Chang Wan Lim, Jun Yeop Lee, Kwang Eun Jung, Jong Eun Won, Byung-Man Kwak, Ki Woong Lee, Jin Ju Park, and Sang Hoon Lee. Journal of the Korean Society of Food Science and Nutrition 2022;51:419-27. https://doi.org/10.3746/jkfn.2022.51.5.419