Screening, Identification, and Application of Dominant Acetic Acid Bacteria for Grape Vinegar Fermentation

In this study, acetic acid bacteria suitable for grape vinegar fermentation were sought to be identified and characterized. Strains were isolated from different varieties of grapes collected from seven different regions of the Inner Mongolia Autonomous Region, and were identified based on acid production qualitative tests, physiological and biochemical tests, and 16S recombinant DNA gene sequence analysis. Evaluation of the fermentation characteristics of the acetic acid bacteria, namely, ethanol, low pH, acetic acid tolerances, and acid production. Finally, the acetic acid bacteria were used to brew grape vinegar, and the fermented grape vinegar was subjected to the determination of organic acids, the analysis of electronic nose detection and sensory evaluation. In total, 71 acid-producing strains were isolated. From these, four acetic acid bacterial strains were successfully identified, namely, the Acetobacter pasteurianus strains DJN2 and XHN1, the TA3 strain of Acetobacter oryzoeni, and the XM1 strain of Acetobacter oryzifermentans. Among these strains, DJN2, XHN1, and XM1 showed overall good tolerance (to 11% anhydrous ethanol, a minimum pH2.8, and 3% glacial acetic acid) and good levels of acid production (more than 41 g/L). In the fermented grape vinegar produced using the three selected strains, six types of organic acid, namely, acetic, malic, tartaric, citric, succinic, and lactic acids were detected. Compared with the grape vinegar fermented using the commercial acetic acid bacterial strain AS1.41, three groups of the grape vinegars fermented using the newly isolated strains were characterized by stronger response values, as determined using electronic nose sensors, and had richer odor types. The aroma of these grape vinegars is rich, and they have a unique sour-sweet fruity taste. This study will provide a basis for the development of novel grape vinegar fermentative strains and contribute to the improvement of grape vinegar quality.