Regular articleExpression of Piromyces rhizinflata cellulase in marine Aspergillus niger to enhance halostable cellulase activity by adjusting enzyme-composition

•P. rhizinflata cellulase expression increased endoglucanase and exoglucanase activity.•FPA of the transformant was 7.44 folds higher of the original strain.•Cellulase from the transformant remained the halostable ability.•Cellulase from the transformant hydrolyzed efficiently cellulose at high salinity.

Cellulase is a complex enzyme consisted of exoglucanase, endoglucanase and β-glucosidase. An enzyme composition affects the synergistic activity. To enhance the activity of halostable cellulase from a marine Aspergillus niger, activities of three enzyme compositions were analyzed respectively. It was found that endoglucanase and exoglucanase in the cellulase had the relative low activities corresponding to β-glucosidase. Thus, an expression system of cellulase in the marine A. niger was constructed. Piromyces rhizinflata cellulase was efficiently expressed by a constructed vector with promoter glaA. Exoglucanase and endoglucanase was increased from 0.21 U/ml and 4.51 U/ml of the original strain to 0.81 U/ml and 19.10 U/ml of the transformant, respectively. FPA increased nearly 7.5 folds from 0.63 U/ml to 4.69 U/ml. Glucose released by hydrolyzing wheat straw with cellulase from the transformant was 1.68 folds higher than that with cellulase from the original strain under high salinity condition. The results illustrated that P. rhizinflata cellulase could be well expressed in marine A. niger. The cellulase from the transformant not only showed higher activity but also remained the halostable ability, indicating that an appreciate proportion of enzyme-composition in cellulase was very important to cellulase activity.