White rot fungi is capable of oxidizing many persistent organic pollutants including dyes. The application of the fungi has been limited for wastewater treatment under non-sterile conditions due to the contamination by bacteria and other micro-organisms. We developed a treatment approach by using immobilized white rot fungi Phanerochaete chrysosporium to degrade reactive dye K-2BP under nonsterile condition. Four different inert carriers were tested for immobilization of the white rot fungi with orthogonal experiments in comparison with suspension culture. The activity of manganese peroxidase (MnP) was used for the evaluation of oxidization performance in order to understand whether contamination of bacteria and other micro-organisms was suppressed. Under non-sterile conditions, the immobilized fungal cultures successfully restrained the growth of microzymes, coccies, and bacillus but suspension culture was highly contaminated with poor MnP activity. Under non-sterile conditions, higher MnP enzymatic activity (690 U/L vs. 125 U/L), higher decolorization efficiency (93.5% vs. 15%) and shorter reaction period (3 days vs. 6 days) were achieved in immobilized cultures in comparison with suspension culture. With the immobilized fungal cultures, no difference was observed under non-sterile and sterile conditions for the degradation of reactive dye K-2BP.

In order to explore ways for the application of white rot fungus in dye effluent treatment under non-sterile conditions, experiment on decolorization of reactive brilliant red was carried out, employing nitrogen-limited and carbon-limited medium with C/N ratio of 56/2.2 and 28/44 (in mmol/L), respectively. The results showed that the decolorization rate reached 92% while culturing white rot fungus with nitrogen-limited medium; however, the decolorization process ended in carbon-limited medium (n(C)/n(N) = 28/44) because of bacterial contamination. In addition, pH rose up to 9.31 after 4 d of decolorization, which was caused by bacterial contamination in the carbon-limited system. Therefore, it is concluded that nitrogen-limited medium can inhibit bacterial growth to some extent while carbon-limited medium is more easily contaminated by bacteria. Nitrogen-limited medium is more suitable in culture of white rot fungus for decolorization of reactive dye. Medium with the ability of inhibiting yeast growth should be developed by adjusting other components of nitrogen-limited medium.

Almost all the studies both domestic and international using white rot fungus for bye wastewater treatment are performed under sterile conditions. However, it is obviously unpractical that wastewater with dyes is treated under sterile conditions. A feasible study was made for using white rot fungus phanerochaete chrysosporium to degrade reactive brilliant red L-2BP dye under non-sterile conditions. The results showed that there was no decolorizing effect under non-sterile condition if white rot fungus was incubated under non-sterile condition, and the decolorization was always near to 0% during decolorizing test for 3 d; in the meantime, a lot of yeast funguses were found in liquid medium when white rot fumgus was incubated under non-sterile conditions; however, if white rot fungus was incubated under sterile condition firstly, its decolorization was above 90% under non-sterile condition, which was similar to that of sterile condition. So we point out that the treating process for wastewater with dyes should be divided into two stage. The first stage is that white rot fungus should be incubated under stcrile conditions, and the second stage is that reactive brilliant red K-2BP is decolorized under non-sterile conditions. The method not only save that operation cost which decolorizing reactive brilliant red K-2BP under sterile condition, but also provide that feasibility for using white rot fungus to degrade wastewater with dyes udder non-sterile conditions.