Acetic Acid Bacteria and the Production and Quality of Wine Vinegar

The production of vinegar depends on an oxidation process that is mainly performed by acetic acid bacteria. Despite the different methods of vinegar production (more or less designated as either “fast” or “traditional”), the use of pure starter cultures remains far from being a reality. Uncontrolled mixed cultures are normally used, but this review proposes the use of controlled mixed cultures. The acetic acid bacteria species determine the quality of vinegar, although the final quality is a combined result of technological process, wood contact, and aging. This discussion centers on wine vinegar and evaluates the effects of these different processes on its chemical and sensory properties

Bioactive compounds derived from the yeast metabolism of aromatic amino acids during alcoholic fermentation

Metabolites resulting from nitrogen metabolism in yeast are currently found in some fermented beverages such as wine and beer. Their study has recently attracted the attention of researchers. Some metabolites derived from aromatic amino acids are bioactive compounds that can behave as hormones or even mimic their role in humans and may also act as regulators in yeast. Although the metabolic pathways for their formation are well known, the physiological significance is still far from being understood. The understanding of this relevance will be a key element in managing the production of these compounds under controlled conditions, to offer fermented food with specific enrichment in these compounds or even to use the yeast as nutritional complement

Estudio comparativo del consumo de aminoácidos y amonio en acetificaciones con cultivo superficial y amonio en acetificaciones con cultivo superficial y sumergido

Se han estudiado los cambios en el contenido de aminoácidos y amonio durante diferentes procesos de acetificación de tres vinos tintos mediante cultivo superficial y cultivo sumergido (8 acetificaciones superficiales y 3 sumergidas). Se tomaron muestras al inicio y al final de las mismas. La determinación de aminoácidos y amonio se realizó por CLAE-fluorescencia empleando AQC como agente de derivatización precolumna. Este método, validado satisfactoriamente, demostró su utilidad para el análisis rutinario de dichos compuestos durante la acetificación. Los resultados mostraron que al inicio de la acetificación el aminoácido más abundante fue prolina seguido de arginina. Se observó un comportamiento diferente entre los dos métodos de acetificación, siendo mucho menor el consumo de aminoácidos en la acetificación sumergida que en la superficial. En esta última, el más consumido fue la prolina, siendo la arginina la principal fuente de nitrógeno en los sistemas sumergidos, lo cual parece estar relacionado con la especie de bacterias acéticas implicadas en el proceso. Además, parece existir cierta correlación entre requerimiento de nitrógeno de estas bacterias y duración del proceso de acetificación

Revalorization of strawberry surpluses by bio-transforming its glucose content into gluconic acid

DOI: 10.1016/j.fbp.2016.05.005 URL: http://www.sciencedirect.com/science/article/pii/S0960308516300372Modern societies produce massive surpluses of food, by-products and wastes that increase the interest for their revalorization. This work examines the use of a culture of Gluconobacter japonicus CECT 8443, without pH control, to convert selectively the glucose content of industrially pasteurized strawberry purée into gluconic acid for the development of new beverages. However, depending on the initial concentration of glucose, the microorganism could transform the acid formed into other compounds; for this reason, in this work the effect of initial sugar concentration on the preservation of the acid was investigated. The results show that the gluconic acid formed in strawberry purée containing no added sugars started to disappear after glucose depletion, but the acid concentration remained constant if sugar-enriched purée was used. The use of this industrial substrate resulted in the presence of yeasts and hence in some fructose uptake; however, the fructose consumption was negligible until after 20-30 h. The use of food by-products is an excellent opportunity not only to recover valuable compounds but for the development of new chemical and biotechnological approaches for their revalorization. This strategy should improve regional economies and contribute to a sustainable management of these underexploited resources

Determination of dehydrogenase activities involved in D-glucose oxidation in Gluconobacter and Acetobacter strains

DOI: 10.3389/fmicb.2016.01358 Link: http://journal.frontiersin.org/article/10.3389/fmicb.2016.01358/full Filiació URV: SI Inclòs a la Memòria: SIAcetic acid bacteria (AAB) are known for rapid and incomplete oxidation of an extensively variety of alcohols and carbohydrates, resulting in the accumulation of organic acids as the final products. These oxidative fermentations in AAB are catalyzed by PQQ- or FAD- dependent membrane-bound dehydrogenases. In the present study, the enzyme activity of the membrane-bound dehydrogenases [membrane-bound PQQ-glucose dehydrogenase (mGDH), D-gluconate dehydrogenase (GADH) and membrane-bound glycerol dehydrogenase (GLDH)] involved in the oxidation of D-glucose and D-gluconic acid (GA) was determined in six strains of three different species of AAB (three natural and three type strains). Moreover, the effect of these activities on the production of related metabolites [GA, 2-keto-D-gluconic acid (2KGA) and 5-keto-D-gluconic acid (5KGA)] was analyzed. The natural strains belonging to Gluconobacter showed a high mGDH activity and low activity in GADH and GLDH, whereas the Acetobacter malorum strain presented low activity in the three enzymes. Nevertheless, no correlation was observed between the activity of these enzymes and the concentration of the corresponding metabolites. In fact, all the tested strains were able to oxidize D-glucose to GA, being maximal at the late exponential phase of the AAB growth (24 h), which coincided with D-glucose exhaustion and the maximum mGDH activity. Instead, only some of the tested strains were capable of producing 2KGA and/or 5KGA. In the case of Gluconobacter oxydans strains, no 2KGA production was detected which is related to the absence of GADH activity after 24 h, while in the remaining strains, detection of GADH activity after 24 h resulted in a high accumulation of 2KGA. Therefore, it is possible to choose the best strain depending on th

Cellulose production and cellulose synthase gene detection in acetic acid bacteria

The ability of acetic acid bacteria (AAB) to produce cellulose has gained much industrial interest due to the physical and chemical characteristics of bacterial cellulose. The production of cellulose occurs in the presence of oxygen and in a glucose-containing medium, but it can also occur during vinegar elaboration by the traditional method. The vinegar biofilm produced by AAB on the air-liquid interface is primarily composed of cellulose and maintains the cells in close contact with oxygen. In this study, we screened for the ability of AAB to produce cellulose using different carbon sources in the presence or absence of ethanol. The presence of cellulose in biofilms was confirmed using the fluorochrome Calcofluor by microscopy. Moreover, the process of biofilm formation was monitored under epifluorescence microscopy using the Live/Dead BacLight Kit. A total of 77 AAB strains belonging to 35 species of Acetobacter, Komagataeibacter, Gluconacetobacter, and Gluconobacter were analysed, and 30 strains were able to produce a cellulose biofilm in at least one condition. This cellulose production was correlated with the PCR amplification of the bcsA gene that encodes cellulose synthase. A total of eight degenerated primers were designed, resulting in one primer pair that was able to detect the presence of this gene in 27 AAB strains, 26 of which formed cellulose. © 2014, Springer-Verlag Berlin Heidelberg

Espacios y destinos turísticos en tiempos de globalización y crisis

2 volúmenesXII Coloquio de Geografía del Turismo, Ocio y Recreación de la Asociación de Geógrafos Españoles. Colmenarejo (Madrid), del 17 al 19 de junio de 2010.Este libro ha sido editado con la colaboración económica del Ministerio de Ciencia e Innovación (ref. CS02010-10416-E)