Medium optimization of ε-polylysine production by response surface analysis

In order to enhance the concentration of e-polylysine(e-PL) with Streptomyces albulus ZC7,response surface methodology were used to optimize the fermentation medium.A Plackett-Burman de-sign was used to evaluate the influence of eight factors firstly.Results showed that the concentration of glucose,yeast extract and(NH4)2SO4 played important roles in influencing the content of e-PL.Then,the path of steepest ascent and the Box-Behnken design were adopted for further optimization,and the optimum concentration levels and the relationships among these factors was found out by quadratic re-gression model equation with Design-Expert statistic methods,the optimal concentration of the vari-ables were determined as: glucose 37.22 g/L,yeast extract 6.9 g/L,(NH4)2SO4 6.55 g/L.Under such conditions,the concentration of e-PL was increased to 8.11 g/L,which was 24.6% higher than the maximum value in the single factor tests.