Optimization of Fermentation Medium for Genetically Engineered Strain with Camel Chymosin-producing capability
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Abstract:
Chymosin can specifically cleave the peptide bond between κ-casein Phe 105 and Met 106 in milk, cause milk-clotting and widely used in dairy products. Bovine chymosi has been deeply studied, but few research on camel chymosin were reported. According to the single-factor experiments design, Plackett-Burman design was used to evaluate the effects of 8 medium components on the production of chymosin to obtain a high-performance fermentation medium. The results showed that glucose, corn syrup, and urea concentrations had significant effects on the chymosin production. Box-Behnken experimental design was employed to optimize the three medium components furtherly. The optimal fermentation medium for antifungal substance production was composed of glucose 86.6 g/L, corn syrup 56.9 g/L, yeast extract 4g/L , KH2PO4 3 g/L, urea 18 g/L, ZnSO4 3 g/L, (NH4)2SO4 1 g/L and MgCl2 0.3 g/L. Under the optimal conditions, the activity of chymosin could reach 431.25 SU/mL, which were 2.08 folds higher than the original medium (207.03 SU/mL). The chymosin activity reached 530 SU/mL after fermentation in an 1Lfermentation tank with exact medium components,being 1.22 folds higher than the chymosin activity obtained by shake flask fermentation.
