Screening of high-yield cellulase mutant by microwave-NTG mutagenesis

The original strain aspergillus niger D2 producing cellulase was treated with microwave irradiation and nitrosoguanidine(NTG).A mutant N14 had higher and stable production of cellulase was obtained.The optimum pH and temperature of the strain were 5.0～6.0 and 28～30℃,respectively.The optimal pH and temperature of enzymatic hydrolysis reaction were 5.0 and 50℃ respectively.In additions,the optimum liquid fermentation conditions of the mutant N14 were obtained through single factor and orthogonal experiment as followed:carbon source bran,nitrogen source yeast extract,the ratio of carbon and nitrogen 4 ∶1,the initial pH 6.5,the inoculum 6%(v/v),the culture temperature 30℃,the culture time 3 d.Under these conditions,the FPA enzyme activity of the mutant reached 363.5 U/ml,which was 2.5 times higher than that of the original strain D2.