In order to improve the cell yeild of recombinant Pichia pastoris during fermentation of glycerol growth stage, the Placket-Burman and Box-Behnken design were applied to optimize the fermentation medium (BMGY). Three variables (yeast extra, peptone and glycerol) which were proved to have significant effects on dry cell weight (DCW) were selected from six variables by Placket-Burman design. Through Box-Behnken design Regression coefficients analysis, a secondary degree polynomial equation was established, and the optimum levels of the three variables were as following: yeast extra 1.13%, peptone 1.61% and glycerol 0.86%. From the 3D response surface plots and 2D contour plots created by the Box-Behnken design, we can also observed the interaction between yeast extra and peptone or yeast extra and glycerol are significant. An average 4.41 g/l DCW after 12 h cultivation in the optimized BMGY media could be attained by the validation experiments, which was 20.6% higher than the formal yield of 3.50 g/l.
Fermentation, Optimization, Placket-Burman design, Response surface methodology
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