Improvement of Fungal Cellulase Production by Mutation and Optimization of Solid State Fermentation

Abstract

Spores of Aspergillus sp. SU14 were treated repeatedly and sequentially with Co60 γ-rays, ultraviolet irradiation, and N-methyl-N′-nitro-N-nitrosoguanidine. One selected mutant strain, Aspergillus sp. SU14-M15, produced cellulase in a yield 2.2-fold exceeding that of the wild type. Optimal conditions for the production of cellulase by the mutant fungal strain using solid-state fermentation were examined. The medium consisted of wheat-bran supplemented with 1% (w/w) urea or NH4Cl, 1% (w/w) rice starch, 2.5mM MgCl2, and 0.05% (v/w) Tween 80. Optimal moisture content and initial pH was 50% (v/w) and 3.5, respectively, and optimal aeration area was 3/100 (inoculated wheat bran/container). The medium was inoculated with 25% 48 hr seeding culture and fermented at 35°C for 3 days. The resulting cellulase yield was 8.5-fold more than that of the wild type strain grown on the basal wheat bran medium.