关键词: 纤维素酶, 液体发酵, 黑曲霉, 优化, 响应面法

Abstract:

Response surface methodology was used to optimize the fermentation conditions for cellulase production by
Aspergillus niger to obtain the maximum carboxymethyl cellulase (CMCase) activity. By one-factor-at-a-time designs, we found
the optimum fermentation conditions to be inoculum age of 24 h and incoculum amount of 10%, and 30 mL of culture medium
composed of 2 g/100 mL glucose, 1 g/100 mL yeast extract and 0.1% PEG at initial pH 7.0 filled in a 250-mL triangular flask.
Inoculum amount and glucose concentration were identified by Plackett-Burman (PB) design as main factors that influence
CMCase activity, and their optimal regions were approached by the steepest ascent path. Finally, using central composite design
and response surface analysis, the optimal fermentation medium was determined as 37.5 mL of a modified PDA medium consisting
of 2.7 g/100 mL glucose, 1.25 g/100 mL yeast extract and 0.1 g/100 mL PEG in a 250-mL triangular flask, and the optimal
fermentation conditions were 8% (3.3 mL), 7.0, 28 ℃, 150 r/min and 96 h for inoculums size, initial pH, temperature, shaking
speed and time, respectively. The maximum CMCase activity under the optimized conditions was (63.5 ± 1.7) U/mL, indicating a
29.59% increase compared to (49.0 ± 1.7) U/mL obtained under the conditions of 30 mL of PDA with 2% glucose at initial pH of 7.0 in
a 250-mL triangular flask, 10% (3 mL) inoculum size with an age of 24 h, and culture at 28 ℃ for 96 h with a shaking speed of 150 r/min.

Key words: cellulase, liquid-state fermentation, Aspergillus niger, optimization, response surface methodology