Abstract: The major fermentation medium components for isomaltooligosaccharide production by Aspergillus niger CU-1 were optimized by full factorial, steepest ascent and Box-Behnken designs. The optimal medium components were determined to be 4% wheat bran extract, 19.67 g/L corn steep liquor, 2.24 g/L NaNO3, and 250 g/L saccharified cassava starch. Fermentation of the optimized medium by Aspergillus niger CU-1 was carried out in a 3.6 L fermenter to obtain isomaltose, panose and isomaltotriose yield as high as 37.4%, an isomaltooligosaccharide yield as high as 83.1%. The good agreement between the predictive and actual values indicated that the mathematical model established based on Box-Behnken design was valid.

Key words: Aspergillus niger, α-glucosidase, response surface methodology, medium optimization, isomaltooligosaccharides