Optimization of streptomyces sp.A11 medium cultivation on cyclo(tyrosyl-prolyl) production using the response surface methodology

The response surface methodology is a three factorial design which provides the relationship between one or more measured dependent response and a number of input (independent) factors. Response surface methodology was used for optimization of fermentation medium for antibacterial agent cyclo(tyr-pro) production by Streptomyces sp A11. The optimal response region of the significant factor was predicted by using a second order polynomial model fitted to the results obtained by applying the Central Composite Design (CCD) statistical design. Determination of the best production medium of cyclo(tyr-pro) showed among 6 carbon sources used, dextrin produced the highest cyclo(tyr-pro). Among the five nitrogen sources used, peptone produced the highest cyclo(tyr-pro), and the mineral salts group I produced the highest cyclo(tyr-pro) compared with others. The results of optimization showed that three variables (dextrin as a carbon source, peptone as nitrogen source, and mixture of mineral salts) used showed significantly affected to the activity of cyclo(tyr-pro). The mathematical model used, obtained by the composition of the three variables most optimum were concentration of dextrin was 32.55 g.L-1 , peptone concentration was 11.22 g.L-1 , and 8.65 mL of mineral salts. By using the composition of mathematic model, cyclo(tyr-pro) was obtained 51.54 mg.L-1 (model expectations) and 50.04 mg.L-1 from experiments. The differences of experiment with expectation response value was 2.91%. Using the optimized parameters, the studies demonstrated an increase in the cyclo(tyr-pro) was 2.5 fold from 20 mg.L-1 to 50 mg.L-1 .