Strain improvement of Acremonium cellulolyticus for cellulase production by mutation

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 β-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 °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 β-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.