The bioactivity of swollenin is beneficial to cellulose decomposition by cellulase despite the lack of hydrolytic activity itself. In order to improve the productivity of swollenin, the effects of culture conditions on the expression level in recombinant Aspergillus oryzae were investigated systematically. With regard to the bioactivity of swollenin, glycerin and peanut meal were the optimal carbon or nitrogen source, respectively. The highest level production of swollenin (50 mg L(-1)) was attained after 88 h cultivation with the initial pH of 5.6 in the culture medium. Then the soluble swollenin was effectively purified from the cultural supernatant by ammonium sulfate precipitation and cationic exchange chromatography with recovery yield of 53.2%. The purified swollenin was fully bioactive due to its strong synergistic activity with cellulose.