Optimization of the Acetification Stage in the Production of Wine Vinegar by Use of Two Serial Bioreactors

Abstract

In the scope of a broader study about wine acetification, previous works concluded that using a single bioreactor hindered simultaneously reaching high productivities with high substrate consumption and the use of two serially arranged bioreactors (TSAB) could achieve such goal. Then, the aim of this work is the optimization, using Karush–Kuhn–Tucker (KKT) conditions, of this TSAB using polynomial models previously obtained. The ranges for the operational variables leading to either maximum and minimum mean rate of acetification of 0.11 ≤ (rA)global ≤ 0.27 g acetic acid·(100 mL·h)−1 and acetic acid production of 14.7 ≤ Pm ≤ 36.6 g acetic acid·h−1 were identified; the results show that simultaneously maximizing (rA)global and Pm is not possible so, depending on the specific objective, different operational ranges must be used. Additionally, it is possible to reach a productivity close to the maximum one (34.6 ≤ Pm ≤ 35.5 g acetic acid·h−1) with an almost complete substrate use [0.2% ≤ Eu2 ≤ 1.5% (v/v)]. Finally, comparing the performance of the bioreactors operating in series and in parallel revealed that the former choice resulted in greater production.

Latest Trends in Industrial Vinegar Production and the Role of Acetic Acid Bacteria: Classification, Metabolism, and Applications—A Comprehensive Review

“…Vinegar elaboration can be carried out by either solid-state fermentation (SSF) or liquid fermentation, with the latter including numerous techniques implemented in Western and European countries, mainly surface and submerged cultures [5,7]. The submerged culture is one of the main systems used to produce vinegar on an industrial scale [7][8][9]52].…”

“…This system also allows for obtaining high-strength vinegars that may reach high acidity levels [up to 15% (w/v)]. With the high demand for these products, it may be necessary to use dual-stage high-strength processes in which two fermentation tanks are operated in a synchronous mode, thus even achieving acetic acid concentrations above 20% (w/v) [9]. In this way, the stressful environment to which AAB are subjected detracts from the overall acetification rate [5].…”

“…Despite the high quality of the final products obtained through traditional systems, including mainly solid-state fermentation and surface culture, their numerous disadvantages, including low efficiency, the slowness of the process, and a lack of control of the operating conditions, have led to the use of the submerged culture system [7,8]. The success of this method, widely implemented in Western and European countries, lies in the high yield and speed of the process under controlled stirring conditions due to the efficiency of mass transfer and continuous vigorous aeration [7,9]. In this sense, the choice of a working mode for the acetators also ensures a suitable environment for the development and activity of AAB, and the control and monitoring of fermentation conditions are some of the fundamental aspects to consider [5,7,10].…”

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“…Vinegar is likely one of the most appreciated products in the fermented food industry and one of the most economically important products obtained from AAB [ 5 , 9 ]. For this reason, among others, much of the research on the metabolism of AAB is aimed at improving the procedures for obtaining this product [ 10 , 11 , 12 ]. Because diverse AAB species may also metabolize sugars and sugar alcohols, the role of membrane-bound soluble dehydrogenases is attracting increasing interest from researchers.…”

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“…Examples of studies that we could classify in this context can be found in other publications of this book. For example, [8,9] deal with the study and modeling of an alternative way of working in the acetification stage of the wine vinegar bioprocess, a product with multiple uses and great importance: For instance, it is a high-quality condiment. For another example, see the publication [10], which deals with the study of the influence of operational variables, temperature, and time on the properties and durability of the processing of another food, sous vide chicken breast fillets; this case is an example of the need to optimize processing conditions in order to reduce the generation of waste from food that has already been prepared and not consumed.…”