Statistical Optimizing of Medium for Clavulanic Acid Production by Streptomyces clavuligerus Using Response Surface Methodology

Clavulanic acid (CA) is a naturally occurring antibiotic produced by Streptomyces clavuligerus. Statistical optimization of the fermentation medium for CA production by Streptomyces clavuligerus was carried out. Multiple carbon sources, glycerol, dextrin, and triolein, were considered simultaneously. A two-level fractional factorial design experiment was conducted to identify the significant components of medium on CA production. Statistical analysis of the results showed that soybean meal, dextrin, and triolein were the most significant medium ingredients on CA production. The optimal level of these screened components was obtained by RSM based on the result of a Box-Behnken design, in which the values of dextrin, soybean meal, and triolein in CA fermentation medium were 12.37 g/L, 39.75 g/L, and 26.98 ml/L, respectively. Using the proposed optimized medium, the model predicted 938 mg/L of CA level and via experimental rechecking the model, 946 mg/L of CA level was attained in shake flask fermentation, significantly high than 630 mg/L of original medium. The optimized medium was further verified in 50-L stirred fermenter, and compared with performance of original medium in parallel, CA titer was increased from 889 to 1310 mg/L; a 47% increase was achieved through medium optimization by statistical approaches.