Dissolved Carbon Dioxide Effects on Glucoamylase Synthesis of Aspergillus niger in Batch and Chemostat Cultures
WANG Li-qun;LU Hong-zhong;CHU Ju;WANG Yong-hong;State Key Laboratory of Bioreactor Engineering,East China University of Science and Technology;
The effect of different levels of elevated dissolved CO_2 availability( CO_2 stress) was investigated in batch and chemostat cultures of Aspergillus niger by gassing with CO_2-enriched air. Under batch cultures,higher elevated dissolved CO_2 availability in culture medium resulted in a more significant decrease in specific growth rate,whereas it appeared to have a positive effect on glucoamylase synthesis. Under chemostat cultures with low dilution rate( D_1= 0. 05 / h),high levels of dissolved CO_2 led to no reduction of specific growth rate,but an increase of glucoamylase production. Whereas at high dilution rate( D_2= 0. 08 / h),both substrate uptake and cell grow were more severely inhibited by more elevated dissolved CO_2. The effect of elevated dissolved CO_2 availability on the fermentation process depends on CO_2 levels as well as dilution rate. Therefore,the influence of carbon dioxide on cell growth and glucoamylase production dependent on CO_2 levels,cultivation mode and specific metabolic activity, which would be helpful for the design of specific growth rate in scale-up of glucoamylase fermentation by Aspergillus niger.