Estimation of the biodegradation rate of 2,3,7,8-tetrachlorodibenzo-p-dioxin by using dioxin-degrading fungus, Pseudallescheria boydii.

We are developing a bioreactor system for treating dioxin-contaminated soil or water using the dioxin-degrading fungus, Pseudallescheria boydii (P. boydii). In order to design the bioreactor system, this study estimated the rate at which P. boydii degraded 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), which is the most toxic of the dioxins. The experimental results showed that P. boydii degraded 2,3,7,8-TCDD during its logarithmic growth phase, using glucose as a carbon source for growth, and that the growth of P. boydii was not affected by 2,3,7,8-TCDD concentrations usually found at contaminated sites. These results were then used to apply successfully an existing mathematical model to the degradation of 2,3,7,8-TCDD by P. boydii. This allowed an estimation of the rate of degradation of 2,3,7,8-TCDD by P. boydii that can be used in the design of the bioreactor system.