Optimization of fermentation medium for steffimycin B production by Box-Behnken response surface methodology

Abstract:

[Background] Streptomyces scabrisporus HBERC-53204 is an actinomycete strain isolated from a soil sample collected in Hunan province.It produces an active compound steffimycin B (SMB) with strong biological activity against a variety of animal and plant pathogens.[Objective] To improve the productivity of the strain for SMB and broaden the research and application of SMB in agriculture and animal husbandry.[Methods] We determined the optimum concentrations of main components including carbon-,nitrogen-containing nutrients and inorganic salts in the fermentation medium to increase the production of SMB by S. scabrisporus HBERC-53204 through single factor experiments.On the basis of the results of single factor experiments,the factors significantly affecting the production of SMB were screened out through Plackett-Burman (PB) design.On the basis of the steepest ascent design and Box-Behnken (BB) design,the medium for the production of SMB was optimized by response surface methodology through fitting the nonlinear equation of significant factors with the yield of SMB.[Results] The composition of the medium for the production of SMB by HBERC-53204 was optimized as follows:glucose 36.22 g/L,peptone 8.00 g/L,yeast powder 8.51 g/L,acid hydrolyzed casein 1.50 g/L,MgSO₄ 0.68 g/L,and KNO₃ 1.00 g/L.The yield of SMB produced in the optimized medium reached 477.26 mg/L in shake flask fermentation,which was 1 773.08% higher than that of the original medium.At the time point of 120 h of fermentation in a 20 L fermenter,the yield of SMB reached a maximum of 214.48 mg/L.[Conclusion] After optimization of the fermentation medium of strain HBERC-53204,the yield of SMB was significantly increased,which was scaled up in a 20 L fermenter.Based on this study,grams of purified SMB compound were obtained.