A novel bioreactor was developed for glucoamylase production in solid state fermentation using Aspergillus niger. Glass columns of different diameter were placed vertically and packed with pre-inoculated substrate and with substrate bed heights in the range 4.5-22.0 cm. Moist air was passed through the bottom of the bioreactor at 1 - 1.5 vvm and fermentation was carried out for 48 h at 30 +/- 1 degrees C. A column packed to a bed height of 18 cm produced about 50% more enzyme (in 48 h) than flask experiments. There was a significant difference between different segments of the columns in growth, enzyme synthesis and sporulation pattern.