Acetic Acid Bacteria in Fermented Food and Beverage Ecosystems

Abstract

Acetic acid bacteria (AAB) are mainly associated with the biotechnological process of vinegar and cellulose production, and although their occurrence in natural fermentation systems has been substantiated, their role remains rather unclear. Members of the Acetobacteraceae phylogenetic group have been reported in a range of spontaneous fermentations, such as the last phase of the cocoa bean fermentation process, the manufacturing of acidic beers, and several other slightly acidic beverages (e.g., kombucha, milk kefir, water kefir). In general, AAB are fastidious and obligate aerobes, although they can remain in a viable but nonculturable state when oxygen levels are low, and thus they are regarded as cumbersome to cultivate or isolate using laboratory media. Currently, with the implementation of culture-independent methods, as well as the introduction of metagenomics and high-throughput sequencing technologies, the abundance and functionalities of AAB in food commodities are being determined. Despite their sporadic isolation or incidence in fermentation ecosystems, the genera Acetobacter, Gluconobacter, Gluconacetobacter, and Komagataeibacter constitute the most frequently encountered taxa. The complete genome sequencing of strains of representative AAB species has elucidated the gene repertoires related to interesting metabolic features, facilitating the understanding of the key role of AAB in natural fermentation ecosystems.