Chinese Journal of Chemical Engineering, Vol.28, No.4, 1120-1128, 2020
Salt-tolerant mechanism of marine Aspergillus niger cellulase cocktail and improvement of its activity
The cellulase cocktail produced by marine Aspergillus niger exhibits a property of salt-tolerance, which is of great potential in cellulose degradation in high salt environment. In order to explain the mechanism on the salt-tolerance of the cellulase cocktail produced by marine A. niger, six cellulase components (AnCel6, AnCel7A, AnCel7B, AnEGL, AnBGL1 and AnBGL2) were obtained by directed expression. Studies on their enzymatic properties revealed that one beta-glucosidase (AnBGL2) and one endoglucanase (AnEGL) exhibited an outstanding salt-tolerant property, and one cellobiohydrolase (AnCel7B) exhibited a certain salt-tolerant property. Subsequent study revealed that the salt-tolerant AnEGL and AnCel7B endowed the cellulase cocktail with stronger salt-tolerant property, while the salt-tolerant AnBGL2 had no positive effect. Moreover, after overexpression of AnCel6, AnCe17A, AnCel7B and AnEGL, the activity of cellulase cocktail increased by 80%, 70%, 63% and 68%, respectively. However, the activity of cellulase cocktail was not improved after overexpression of AnBGL1 and AnBGL2. After mixed-strain fermentation with cellobiohydrolase recombinants (cel6a, cel7a and cel7b recombinants) and endoglucanase recombinant (egl recombinant), the the activity of cellulase cocktail increased by 114%, 102% and 91%, respectively. (C) 2019 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.