Application of Polymerase Chain Reaction–Denaturing Gradient Gel Electrophoresis to Resolve Taxonomic Diversity in White Rot Fungus Reactors

Abstract

We analyzed the effect of fungal infection on dye decolorization in continuous and sequential white rot fungus bioreactors. Biological samples of biofilm were collected to determine the ability of these bioreactors to degrade dye in synthetic wastewater. Polymerase chain reaction–denaturing gradient gel electrophoresis was used to analyze the taxonomy of the fungal community. Decolorization rate and manganese peroxidase activity were analyzed. Scanning electron microscopy was used to examine the physical structure of the biofilm. At an influent concentration of 50 mg/L, decolorization rates and chemical oxygen demand (COD) removal rates were as high as 88.7% and 53.7% in the sequential reactor and 85.5% and 54.6% in the continuous reactor on day 6 of the studies, respectively. The quantity of foreign fungi in the reactors increased over time and negatively affected Phanerochaete chrysosporium (PC) growth by competitively absorbing nutrients from the culture medium, resulting in a decline in PC-mediated dye decolorization. Changes in manganese peroxidase activity corresponded to dye decolorization rate. Decolorization capacity of the reactor was dependent on multiple factors including operation mode, operating period, and dye concentration, the latter being the most critical. Polymerase chain reaction–denaturing gradient gel electrophoresis analysis revealed the presence of multiple fungal taxa in some samples. The fungal community was dominated by PC in both reactors. Variations in the makeup of the fungal community corresponded to changes in dye biodegradation. In the sequential reactor, fungal diversity was initially low and progressively increased as treatment progressed, whereas in the continuous reactor the diversity was initially high and then decreased with time. Diversity of foreign fungi was higher in the sequential reactor than in the continuous reactor, suggesting that the latter is more suitable for dye decolorization.