Optimization of glucose oxidase production by Aspergillus niger in a benchtop bioreactor using response surface methodology

Response surface methodology (RSM) was applied to optimize the speed of agitation and the rate of aeration for the maximum production of glucose oxidase ( GOD) by Aspergillus niger. A 2(2) central composite design using RSM was employed in this investigation. A quadratic model for GOD production was obtained. Aeration had more negative effect on GOD production than agitation. Significant negative interaction existed between agitation and aeration. The quadratic term of agitation presented significant positive effect. The maximum level of GOD was achieved when the speed of agitation and the rate of aeration were 756 rev min)(-1) and 0.9 v/v/m, respectively. The fermentation kinetics of GOD by Aspergillus niger were also studied in a batch system. A simple model was proposed using the Logistic equation for growth, the Luedeking-Piret equation for GOD production and Luedeking-Piret-like equation for glucose consumption. The kinetic model parameters X-0, X-m, mu(m), alpha, k, Y-X/S, m(S) and S-0 is 0.24 mg ml(-1), 1.65 mg ml(-1) and 0.23 h(-1), 3.45 U mg(-1), -0.81 U ml(-1), 1.60 g g(-1), 9.72 g g(-1) h(-1) and 97.6 g l(-1), respectively. The model appeared to provide a reasonable description for each parameter during the growth phase. The production of GOD was growth-linked.