Decolorization of azo dyes by free and immobilized bacterial-fungal consortium QM

A developed bacterial-fungal consortium QM consisting of two strains were isolated from textile effluent and identified as Geotrichum candidum and Bacillus cereus. The study of decolorization of azo dyes showed that mixed consortium QM had higher decolorization efficiency than individual strain in a wide range of pH, temperature, dye concentrations and salinity. Decolorization rate of different azo dyes by consortium QM reached above 80% in 24 h. Consortium QM enhanced the decolorization efficiency of azo dye due to synergistic effect between the two strains, which was related to oxidation/reduction potential (ORP) decrease caused by Geotrichum candidum. The UV-Vis and HPLC analysis revealed that azo dye was degraded by the consortium QM. Furthermore, the consortium QM immobilized in alginate beads and nylon sponges was used for repeated-batch and continuous decolorization. It was observed that over 60% azo dyes were removed by immobilized consortium after five cycles of repeated batch decolorization. Immobilized consortium QM could decolorize average 80% dyes in the packed-bed bioreactor with hydraulic retention time (HRT) of 25 h during 20 d of continuous operation. These results showed that consortium QM has a potential for the application of textile effluent decolorization.