Abstract:

Aspergillus niger 08013, showing the highest endoinulinase activity of 3.05 U/mL was screened from 20
Aspergillus niger strains conserved in our laboratory. The results of one factor-at-a-time experiments showed that the
appropriate fermentation conditions were 100 mL of medium in a 250-mL triangular flask, 30 ℃, an inoculum size of
1 cm2/250 mL, shaking at a speed of 180 r/min and pH 5.0. The optimal fermentation conditions were determined by central
composite design and response surface methodology to be 99 mL of medium in a 250-mL triangular flask, 31 ℃, an
inoculum size of 0.99 cm2/250 mL, shaking at a speed of 180 r/min and pH 5.0. Under the optimized conditions, the activity
of endoinulinase produced by the strain 08013 was 6.43 U/mL, which was increased by 111% as compared to the initial
activity before the optimization, 3.05 U/mL.

Key words: inulinase, Aspergillus niger, submerged fermentation, response surface analysis, optimization