Persistence and functions of a decolorizing fungal consortium in a non-sterile biofilm reactor

In this study, a continuous biofilm decolorizing system with high efficiencies of dye degradation and textile wastewater treatment was established using selected fungal consortium. Function and persistence of this fungal consortium were assessed using traditional and molecular biological methods along with near 4 months running process under non-sterile conditions. The microbial cultivation results indicated that the colony forming units (CFUs) ratio of fungi to bacteria stabilized between 51.8:1 and 6.8:1 under the influent conditions of various simulated and real textile wastewater. Clone libraries and phylogenetic trees of bacteria and fungi were respectively constructed based on their full length 16S and partial 26S rRNA gene sequences retrieved from the biofilm at the end of the system running. The results indicated that the dominant population preserved in the system was yeasts belonging to genus Candida. While most of the filamentous fungi isolated from the enrichment consortium could not be preserved on the biofilm. Among the three fungal isolates with high efficiency of dye decolorization, only Candida tropicalis was retrieved and occupied near 70% in the fungal clone library. 26.5% of the retrieved fungal sequences were grouped with some species of Trichoderma which did not exhibit dye decolorization abilities. Compared to the fungal phylogenetic tree, diversity of bacteria was far higher. 67.9% of the retrieved bacterial sequences were clustered into Alphaproteobacteria.