Importance of acetic acid bacteria in food industry

Acetic acid bacteria (AAB) comprise a group of gram-negative or gram-variable, ellipsoidal to rod-shaped cells that have an obligate aerobic metabolism with oxygen as the terminal electron acceptor. In the first classification of AAB, two main genera were determined as Acetobacter and Gluconobacter, but nowadays twelve genera are recognized and accommodated to the family Acetobacteraceae, the Alphaproteobacteria: Acetobacter, Gluconobacter, Acidomonas, Gluconacetobacter, Asaia, Kozakia, Swaminathania, Saccharibacter, Neoasaia, Granulibacter, Tanticharoenia and Ameyamaea. Isolation, purification, identification and preservation of AAB are very difficult. Phenotypic methods based on physiological abilitiesies have been used for identification of AAB by using various media. These phenotypic properties have now been complemented or replaced by molecular techniques, which are DNA and RNA based techniques. AAB are widespread in nature on various plants (fruits, cereals, herbs, etc.). They are important microorganisms in food industry because of their ability to oxidize many types of sugars and alcohols to organic acids as end products during fermentation process. The best known industrial application of AAB is vinegar production. This group of bacteria is also used in cellulose and sorbose production. On the other hand, the oxidizing ability of AAB could have spoilage effect in some products such as in wine. The aim of the present review is to introduce the importance of AAB in food industry by showing their current taxonomy, enumeration, isolation and identification methods, isolation sources and beneficial effects in food production systems.