Culture Medium Optimization by Response Surface Methodology for Enhanced Production of β-glucosidase from Aspergillus Niger

In order to obtain high β-glucosidase productivity from Aspergillus niger M85 fermentation broth,response surface methodology was applied to optimize the key fermentation parameters.Plackett-Burman design was firstly used to screen the significant factors influencing enzyme production,namely wheat bran and MgSO4·7H2O concentration.The path of steepest ascent was further used to approach to the biggest response region of parameters affecting enzyme activity.The best results of combination experiments was wheat bran 17.0 g·L-1,and MgSO4·7H2O 8.0 g·L-1.Central composite design and response surface analysis were applied and a second-order regression equation model with β-glucosidase activity as response value was established to predict enzyme acitivity level.The optimal fermentation parameters were as follows: wheat bran 18.345 g·L-1,and MgSO4·7H2O 7.963 g·L-1.After 4 days fermentation under the optimal conditions,the β-glucosidase activity reached 0.2640 U·mL-1,with an increase of 61.97 % compared to the fermentation with original parameters.The prediction model indicated high reliability,which can be applied to optimization of β-glucosidase fermentation conditions.Enzyme production process showed that β-glucosidase enzyme activity can achieve a maximum of 0.333 4 U·mL-1 after 5 days,while reducing sugars concentration is decreased to 0.49 g·L-1.