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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Considering the limited availability of technology for the production of rice vinegar and also due to the potential consumer product market, this study aimed to use alcoholic fermented rice (rice wine (Oryza sativa L.)) for vinegar production. An alcoholic solution with 6.28% (w/v) ethanol was oxidized by a submerged fermentation process to produce vinegar. The process of acetic acid fermentation occurred at 30 ± 0.3°C in a FRINGS  Acetator (Germany) for the production of vinegar and was followed through 10 cycles. The vinegar had a total acidity of 6.85% (w/v), 0.17% alcohol (w/v), 1.26% (w/v) minerals and 1.78% (w/v) dry extract. The composition of organic acids present in rice vinegar was: cis-aconitic acid (6 mg/L), maleic acid (3 mg/L), trans-aconitic acid (3 mg/L), shikimic + succinic acid (4 mg/L), lactic acid (300 mg/L), formic acid (180 mg/L), oxalic acid (3 mg/L), fumaric acid (3 mg/L) and itaconic acid (1 mg/L).Keywords: submerged fermentation; microfiltration; acetic acid bacteria; vinegar.Practical Application: Vinegar rice produced by a submerged fermentation process from alcoholic fermented rice.

Water kefir is considered to be a functional food with probiotic characteristics. It can be improved with addition of organic brown sugar and fruits native to Brazil, such as jaboticaba. The objective of this study was to evaluate the effects of brown sugar type: organic and conventional and the presence or absence of jaboticaba pulp in water kefir fermentation, based on the carbohydrate, organic acid, mineral composition and color profile. The fermentation process was carried out in two stages: with kefir grains, for 24 hours, at 25 °C and after filtration, maintained for 24 h at 25 °C in hermetic bottles, followed by a period of 8h refrigeration, and monitored every 8 h. Scanning electron microscopy of the kefir grains was performed after 24 h. The major changes in physicochemical patterns occurred up to 40 h. The final beverages presented acidic characteristics as a result of the production of lactic, acetic and succinic acids. The total sugar content had a reduction of around 50%. The sucrose content was reduced and the glucose and fructose increased. The use of organic sugar influenced the composition of the minerals. The characteristics related to color showed a tendency to increase over the evaluated times. It was concluded that it is possible to produce beverages fermented by water kefir grains, using organic or conventional brown sugar and jabuticaba pulp, being an alternative for the substitution of soft drinks, since it has no preservatives or food colorings, presents lower content of sugars and can be handcrafted.

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Rice wine was made from broken rice (by‐product of rice processing), which was hydrolyzed by amylolytic enzymes, producing syrup with high content of dextrose equivalent (51.04% DE). The must presented 164 g/L of glucose (15 ºBx) and pH of 2.67 was fermented for 22 h at 25C by Saccharomyces cerevisiae. Fermented alcoholic (rice wine) reached yield value of 74.94% (Y1), 91.71% (Y2) and productivity (Pp) of 2.85 g/Lh in alcohol, with alcohol concentration of 62.8 g/L, 28.0 g/L of glucose, 2.5 °Bx and pH of 3.0. The kinetic parameters – Yp/s 27.75%, μN 0.008 h−1, gt 3.99 h, PN 0.13 logUFC/mLh – were determined. The wine contained a total of 11 volatile compounds identified by GC‐FID, 7 alcohols (methanol, ethanol, n‐propanol, n‐butanol, iso‐amylic alcohols, iso‐butanol and glycerol), 2 aldehydes (acetaldehyde and acetol), 1 ester (ethyl acetate) and 1 ketone (acetone). Practical Applications The product obtained showed potential features to be employed not only as alcoholic beverage, but also as a raw material in the production of other products such as vinegar, adding value to rice processing. Considering the production outlook and the amount of generated by‐product, it is a lower cost substrate for such application. The characterization of volatile flavor compounds might be made use not only for a better understanding of this new‐type product, but also for the further utilization in other wine or alcohol production.