This paper investigated the influence of using yeast extract, which is the source of redox mediators riboflavin and nicotinamide, in the decolorization of solutions containing the azo dye Drimaren Blue HF-RL in anaerobic conditions. It involved the incubation of serum bottles kept at 25 ºC and inoculated with the azo-dye, and anaerobic sludge in the presence and absence of carbon source (glucose or yeast extract) and redox mediators (riboflavin and yeast extract). The monitoring of color, chemical oxygen demand (COD) and volatile fatty acids (VFA) showed that the addition of yeast extract (0.5 g/L) resulted in 80 to 85% color removal in the first 24 hours of incubation; and that the metabolites of dye degradation were toxic to the anaerobic microorganisms, which led to low COD removal efficiencies either in the presence or absence of yeast extract. The results also showed that the efficiencies of color removal were below 30% in the presence of only glucose or riboflavin, indicating that the yeast extract acted simultaneously as source of carbon and redox mediators.
yeast extract; redox mediators; azo-dyes; volatile fatty acids; anaerobic treatment; industrial effluent
