Aspergillus sp. NR-4201 was assessed by degrading glucosinolates in brown mustard seed meal (Brassica juncea). A liquid culture of the strain, in a medium derived from the meal, produced total degradation of glucosinolates at 32 h. Under these conditions, the glucosinolate-breakdown product, allylcyanide, was formed in culture filtrates. In a plate culture under sterile conditions, the growth of the strain in heat-treated meal media was shown to be effective at 30 degrees C with 51% moisture, as determined by the measurement of the colony growth rate. On the laboratory scale, solid-state culture under the same conditions gave rise to total glucosinolate degradation within 48 h. In comparison, under non-sterile conditions in either heat-treated or non heat-treated meal samples, the degradations were complete after 60 and 96 h, respectively. In these cases, growth was associated with some out-growths of contaminating fungi, mainly Rhizopus sp. and Mucor sp. The glucosinolate-breakdown product, allylcyanide, was not detected in the solid-state meal-media culture presumably due to evaporative loss from the fermentation matrix.