In the search for an efficient producer of cellulolytic enzymes, Acremonium cellulolyticus strain C-1 was subjected to mutagenesis using UV-irradiation and N-methyl-N'nitro-N-nitrosoguanidine (NTG) and strain CF-2612 was isolated. Strain CF-2612 exhibited higher filter paperase (FPase) activities (17.8 U/ml) than the parent strain C-1 (12.3 U/ml). Soluble protein production and beta-glucosidase activity from strain CF-2612 were also significantly improved. FPase activity, cellulase productivity and yield of CF-2612 using batch culture with 5% Solka Floc in a 2-l jar fermentor at 30 degrees C reached 18.0 U/ml, 150.0 FPU/l/h and 360.0 FPU/g carbohydrate, respectively; when fed-batch culture was used with Solka Floc, these values reached 34.6 U/ml, 240.3 FPU/l/h and 346.0 FPU/g carbohydrate, respectively. It was observed that more hydrolyzed glucose was released from pretreated eucalyptus with the enzyme of strain CF-2612, compared with that of the commercial cellulase GC-220. This result was attributed to the higher ratio of beta-glucosidase/FPase activity of strain CF-2612. Three distinguishable phases including the periods of primary or second mycelial growth and mycelial fragmentation were proposed in batch culture by A. cellulolyticus. (C) 2009, The Society for Biotechnology, Japan. All rights reserved.