Application of residual yeast as a source of redox mediators for the anaerobic decolorization of a model azo dye.

Abstract

This work investigated the anaerobic degradation of the model azo dye Remazol Yellow Gold RNL in batch reactors using discharged residual yeast as the source of redox mediators (RM). Two yeast lysis methods (mechanical lysis and sonication) were tested and optimized to produce a riboflavin-rich yeast lysate. The reactors were operated at 25 oC for 48 hours, evaluating the effect of external carbon source (glucose) and RM (from residual yeast lysate and commercial yeast extract) addition. The results showed that color removal efficiencies for the batch reactors fed with commercial yeast extract reached 90%, whereas those fed with discharged yeast lysate reached 80% (sonication) and 73% (mechanical lysis). These values were statistically higher when compared to reactors operating without RM (48 to 66%), demonstrating that yeast extract enhances azo dye degradation in anaerobic conditions and that the residual yeast is a cheap and alternative source of carbon and of the RM riboflavin.