Solid state fermentation (SSF) culture conditions were investigated for the production of feruloyl esterase by Aspergillus niger I-472 and compared with submerged culture conditions. Sugar beet pulp was tested for its ability to be used both as solid support and/or carbon substrate. Mycelial growth was monitored through ergosterol measurements. Under submerged culture conditions, A. niger I-1472 produced esterase active on methyl ester of cinnamic acids, principally methyl ferulate and methyl sinapinate. Under SSF culture conditions, the enzymic profile was different since significant esterase activities using methyl caffeate and methyl p-cournarate as substrate were detected, showing the presence of at least two different proteins. Northern blot analysis of the mycelium clearly indicated the expression of feruloyl esterase gene in both conditions. (C) 2002 Elsevier Science Ltd. All rights reserved.