The group of Gram-negative bacteria capable of oxidising ethanol to acetic acid is called acetic acid bacteria (AAB). They are widespread in nature and play an important role in the production of food and beverages, such as vinegar and kombucha. The ability to oxidise ethanol to acetic acid also allows the unwanted growth of AAB in other fermented beverages, such as wine, cider, beer and functional and soft beverages, causing an undesirable sour taste. These bacteria are also used in the production of other metabolic products, for example, gluconic acid, l-sorbose and bacterial cellulose, with potential applications in the food and biomedical industries. The classification of AAB into distinct genera has undergone several modifications over the last years, based on morphological, physiological and genetic characteristics. Therefore, this review focuses on the history of taxonomy, biochemical aspects and methods of isolation, identification and quantification of AAB, mainly related to those with important biotechnological applications.

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This study aimed to verify the need for minerals and vitamins to increase the production of cell mass by acetic acid bacteria (AAB) isolated from the vinegar industry (086/06) and standard strain (Acetobacter aceti CCT 2565). Five minerals (Mo, B, Zn, Fe, and Mn) and eight vitamins (p-aminobenzoic acid, thiamine, niacin, pantothenic acid, pyridoxine, biotin, cyanocobalamin, and inositol) were tested in a fractional factorial design. To prepare the inoculum, different compositions of MYP (mannitol, yeast, and peptone) medium were tested. The most adequate medium was mannitol 25 g/L, yeast extract 0.625 g/L, and peptone 0.375 g/L. Through contour curves, it was determined that strain 086/06 needed supplementation with minerals Mo, B and Mn and vitamins p-aminobenzoic acid, pyridoxine and cyanocobalamin. Standard strain CCT 2565 needed supplementation of all minerals and vitamins studied, except inositol. The lower requirement of micronutrients for high cell multiplication of the 086/06 strain may be related to the adaptation of strain 086/06 to industrial production conditions.

Research background. Despite the great properties of bacterial cellulose, its manufacture is still limited due to difficulties in production at large-scale. These problems are mainly related to low production yields and high overall costs of the conventional culture media normally used. Reversing these problems makes it necessary to identify new cheap and sustainable carbon sources. Thus, this work aimed to isolate and select a high cellulose-producing Komagataeibacter strain from vinegar industry, and study their potential for bacterial cellulose synthesis in an industrial soybean co-product, known as soybean molasses, to be used as fermentation medium. Experimental approach. For one isolated strain that exhibited high level of cellulose production in the standard Hestrin-Schramm medium, the ability of this biopolymer production in a soybean molasses-based medium was determined. The produced membranes were characterized by thermogravimetric analysis, X-ray diffraction, infrared spectroscopy, water holding capacity and rehydration ratio for determination of its characteristics and properties. The selected strain was also characterized by genetic analysis for determination of its genus and specie. Results and conclusions. An isolated strain was genetically identified as Komagataeibacter intermedius V-05 and exhibited the highest cellulose production in Hestrin-Schramm medium (3.7 g/L). In addition, the production by this strain in soybean molasses-based medium was 10.0 g/L. Membranes from both substrates were similar in terms of chemical structure, crystallinity and thermal degradation. Soybean molasses proved to be a suitable alternative medium for biosynthesis of cellulose in comparison with standard medium. In addition to providing higher production yield, the membranes showed great structural characteristics, similar to those obtained from standard medium. Novelty and scientific contribution. In this research, we have isolated and identified a Komagataeibacter strain which exhibits a high capacity for cellulose production in soybean molasses medium. The isolation and selection of strains with high capacity of microbial metabolites production is important for decreasing bioprocess costs. Furthermore, as there is a necessity today to find cheaper carbon sources that provide microbial products at a lower cost, soybean molasses represents an interesting alternative medium to produce bacterial cellulose prior to its industrial application.