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Capacidad antifúngica de sobrenadantes libres de células obtenidos de la fermentación de un sustrato de “panela” con gránulos de kefir de agua

Water kéfir (WK) is a moderately sour fermented beverage elaborated in sugar-containing solutions through fermentation by a microorganism consortium, principally lactic acid bacteria (LAB) and yeasts, embedded in a matrix of polysaccharide so-called WK grains. The presence of fungi and their toxins it is a problem for the food industry, such as Aspergillus ochraceus and their mycotoxin production especially in coffee and wine. Some alternatives that have been evaluated for their inhibition include lactic acid bacteria and generally fermented products. The main objective was to evaluate the capacity of WK to ferment a Colombian beverage made with Panela and to assess capability of this product to retard the germination of a common toxigenic fungi like Aspergillus ochraceus. 8 cell-free supernatants (CFS) were obtained from separate fermentations and with different organic acids (OA) concentrations (e. g., lactic and acetic). Different fermentations were conducted with WK in Panela broth during 32.5 h periods at 25, 30, and 37°C. We determined the kinetics of acidification of WK along with the corresponding increment in biomass and conducted a quantitation of microorganisms groups that composed the grain. The greatest biomass increase occurred at 25 °C (92%); but the fermentation temperature affected the composition of microorganisms conforming the grain, with the quantity of LAB decreasing at the highest fermentation temperatures (37 °C) (1x10^6 cfu ml-1), compared with the minimum temperature (25 °C) (6x10^7 cfu ml-1). The CFS5 (pH 3.2; fermentation temperature 30 °C) exhibited the greatest antifungal activity. We attribute the inhibitory power of these ferments to the OA produced during fermentation, although we cannot discard the possibility of the action of other substances not specifically quantified. We concluded that WK can grow and fermentate Panela broth and that its CFS can exert an antifungal effect against A. ochraceus

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