Screening And Mutagenesis Breeding Of Terramycin Producing Bacteria

Oxytetracycline (OTC) is an antibiotic produced by fermentation of Streptomyces rimosus.It can be used for the synthesis of doxycycline and as an animal feed additive.Therefore,mutagenesis breeding and fermentation process optimization of Streptomyces rimosus have very important economic benefits.In this study,AGAR block method and coloration method were used to detect terramycin and to screen producing bacteria.AGAR block method is convenient,simple and easy to observe.It is suitable for the initial screening of a large number of strains and greatly improves the screening efficiency.In combination with these two methods,terramycin producing strain B was obtained from soil screening.Starting from strain B,this project USES ultraviolet,microwave,lithium chloride and other mutagenesis factors to treat the spores step by step.After 10 s ultraviolet irradiation of spore solution of strain B,OTC yield of strain UV 5 reached the maximum 10 820 u/m L,which was 20.99 % higher than that of strain B.After 60 s microwave treatment of the spore solution of UV 5 strain,the OTC yield of MW 9 reached the maximum 19 351 u/m L,which was 88.79 % higher than that of UV 5 strain.Because the treatment effect of lithium chloride was not ideal,the subculture was selected after ultraviolet mutagenesis and ultraviolet and microwave mutagenesis.The results showed that the high yield quality of strain MW 9 had good genetic stability.In this study,the fermentation medium formulation and fermentation conditions of MW9 were optimized.The optimal fermentation medium was obtained by single factor experiment: corn starch 120 g/L,yellow bean cake powder 25 g/L,calcium carbonate 12 g/L,ammonium sulfate 15 g/L,sodium chloride 4 g/L,corn pulp 8 g/L,potassium dihydrogen phosphate 0.3 g/L,cobalt chloride 0.01 g/L.The optimal shaking culture conditions: the inoculation amount was 5%,the rotation speed was 220 r /min,the filling amount was 35 m L/250 m L,the initial pH of fermentation medium was 7.0,the culture temperature was31 ?,and the fermentation time was 6 days.Based on the above optimized fermentation process,OTC yield of strain MW 9 reached 28953 u/m L,which was 49.62 % higher than that before optimization.This paper provides a new way to estimate the pot yield and finds a positive correlation between the activity of amylase in seed solution and the final yield.