Abstract:The strain HDFE1, producing feruloyl esterases, was isolated from rotten wood fiber. It was identified as Penicillium citrinum Thom by study of morphology and rDNA ITS1-5.8S-ITS2 sequence and phylogenetic analysis. The optimum conditions for its growth were pH 6.0 and 30oC. At 30oC, pH 6.0, and 200 r/min for 60 h, the strain could produce feruloyl esterases at a yield 25 of 20.75 U/L.