Study On Production Of Fusidic Acid By Strain Breeding And Process Optimization

Fusidic Acid（FA）,a kind of steroidal antibiotics,is isolated from the fermentation broth of Fusidium coccineum fungus,it is mainly active against gram-positive microorganisms.FA has the similar structure to helvolic acid and cephalosporin P1,but more stronger,it is also the only clinical application of the fusidane class.Its unique antibacterial mechanism makes it almost free of cross-resistance with other antibiotics,so FA has a broad application prospect.Currently,FA is mainly produced by microbial fermentation,and there are few related reports at home and abroad.In this study,we aim to improve and stabilize the production of FA through breeding strain and the optimization of fermentation process,so that it can lay a foundation for the industrial production of FA.Firstly,we got a stable characteristic strain ZH08-15（335.5 mg/L）as an original strain through several rounds of natural screening,then ZH08-15 was treated by UV mutation,NTG radiation,ARTP radiation ⁶⁰Co-γradiation and selected by the hypertonic sucrose screening model,after then we obtained a strain of high-yield mutant strains ZH08-γ-17（1206.9mg/L）of which the fermentation unit increased 3.60times compared to the original strain.In order to further increase the yield,we optimized the fermentation process,After optimization,the optimal culture conditions were as follows:slant culture time 7d,the age of the species 48h,the inoculum amount 10%,the initial p H of fermentation medium 6.5,the culture temperature 25℃,and the culture days 8d.The single-factor experiment on fermentation medium showed that nitrogen source had a great influence on the yield of FA,therefore,we optimized fermentation medium（%）through Box-Behnken design（a kind of Response Surface Methodology）as follows:sucrose 14,angel yeast YP601 1.882,soy peptone 0.826,cotton seed meal 0.51,（NH₄）₂SO₄0.1,Mg SO₄·7H₂O 0.2,K₂HPO₄ 0.15,the production of ZH08-γ-17 in which was 1409.4mg/L in shake flask culture,an increase of 16.8%compared with the previous medium.And then,we conducted further study on the fermenter,the fermentation unit of ZH08-γ-17 reached 2114.1mg/L through adjusted inoculum amount,improved dissolved oxygen and added sucrose,that is a 40.4%increase compared to the shake flask culture.Finally,by adjusting the p H of fermentation broth,the concentration was extracted with ethyl acetate,followed by evaporation,and then,the concentration was verified by MS,the result were the same as those reported in the literature,which was determined as FA.