Abstract A solid-state fermentation (SSF) process for the continuous production of the enzyme tannase is currently being developed. This paper describes a laboratory scale prototype reactor that was built with the specific aim in operating continuously with solid substrates and without inoculation of the feed. Mixing, fungal growth and sporulation studies have been conducted as a basis for successful operation of a truly continuous process. The mixing studies at different feed rates revealed a mixing pattern with near perfect mixed flow and the solids mixing in the reactor have been characterised using a dispersion model. Lower biomass, tannase yield and sporulation rate were obtained in a rotating batch culture at 0.7 rpm compared to static batch culture, presumably due to the deleterious effect of shear. The results of this and future research will be used in order to predict operation variables in the continuous SSF process.