Abstract:Three filamentous fungi strains[Strain-1（S-1），Strain-2（S-2），and Strain-3（S-3）]were obtained using enrichment culture，and two rounds of screening using soil samples obtained from Liushuwan forest（Qingjiangpu District，Jiangsu Province，China），with sodium carboxymethylcellulose （CMC-Na）as the only carbon source.Among the three strains，S-2 had the strongest cellulase production ability with an FPA activity of 0.21 U/mL.To improve the cellulase production ability of S-2，the strain was subjected to ultraviolet mutagenesis resulting in the strain SUV2-1.Through single-factor experimentation and response surface experimental design，the fermentation medium for the strain was optimized.The optimal medium for cellulase enzyme production from SUV2-1 contained straw powder（11.63 g/L），peptones（2.33 g/L），and Tween-80（2.71 mL/L）.FPA activity obtained using this medium under shaking flask fermentation conditions was 0.45 U/mL.This represented an FPA activity increase of 51.15%compared with the strain prior to fermentation optimization and a 113.00%increase compared with the original strain prior to mutagenesis.