Medium optimization of α-glucosidase inhibitors production by response surface analysis

Abstract:

[Objective] In order to improve production of α-glucosidase inhibitors from Streptomyces gobitricini PW409, response surface methodology was used to optimize the fermentation medium. [Methods] A Plackett-Burman design was used to evaluate the influence of seven factors firstly. Then, the path of steepest ascent and the Box-Behnken design were adopted for further optimization, the optimum concentration levels and the relationships among these fac-tors was found out by quadratic regression model equation with Design-Expert statistic methods. The concentrations of α-glucosidase inhibitors in the fermentation broth were detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS). [Results] The concentration of soluble starch, KNO3 and K2HPO4 played important roles in influencing the content of inhibitors. The optimal fermentation medium is: soluble starch 9.01 g/L, KNO3 11 g/L, K2HPO4 0.32 g/L, MgSO4?7H2O 0.50 g/L, FeSO4?7H2O 0.01 g/L, pH 7.5. [Conclusion] Under such conditions, the half maximal inhibitory concentration (IC50) of fermentation broth to maltase glucoamylase was 22 mg/L, inhibitory activity increased nearly 10 times. The concentration of 1-deoxynojirimycin and miglitol were increased to 7.84 mg/L and 0.94 mg/L, which was 668 and 10 times higher than before, respectively.