Thanatephorus cueumeris Dec 1, a basidiomycete, is a promising decomposer of several xenobiotics. Air-membrane surface bioreactor culture (AMS culture), a hybrid between solid-state and submerged culture, was used for Dec 1 growth. The optimum temperature for ANIS culture (25 degrees C was lower than that for submerged culture (30 degrees C). Fungal growth was almost the same in AMS culture as in submerged culture at optimum temperatures. However, protein secretion, dye decolorizing peroxidase (DyP) activity, and aryl alcohol oxidase activity, were 18-, 233-, and 36.5-fold higher in AMS culture than in submerged culture, respectively, indicating that AMS culture of Dec 1 was superior to submerged culture. In in vivo dye decolorization tests, 13 of 16 dyes were decolorized by more than 90% within 10 days. Interestingly, under AMS culture, a biofilm was formed; biofilm formation was not, however, essential for DyP and manganese dependent peroxidase (MnP) activities. Although the correlation between DyP activity and water activity was unclear, MnP activity seemed to increase in activity with decreasing water activity, even when no biofilm formation was observed.