Fermentation Process And Stability Research Of A Novel Macrolide Antifungal-antibiotic

In recent years, the infection of deep fungus increases gradually, which threatens sufferers’ health and lives. A marine strain of Bacillus which can produce a kind of macrolide antifungal-antibiotic with high antifungal activity against Canidia albicans was screened. In this paper, the fermentation process, kinetic model, fed-batch culture, antifungal activity and mechanism of a novel antifungal substance from B. subtilis CGMCC4140was studied. Further more, The work is useful for the further development and application of the novel antibiotic.Culture conditions for producing the antibiotic were optimized by single-factor methodology in5L fermenter. The culture conditions were optimized as follows:pH6.5, rotation speed300r/min, broth content60%(v/v), inoculum10%(v/v), aeration rate2.0vvm (volume per volume per minute), soybean oil is the better antifoaming agent, fermentation time24h, the potency activity of culture broth reached to36739.75U/mL, which was1.75-fold compared with the initial conditions. A mathematical model was developed to describe the kinetics of the macrolide antifungal-antibiotic production.The study found that, soybean oil can promote the formation of antibiotic if adding0.5%soybean oil during fermentation process, the potency activity of culture broth add47.5%compared with the initial conditions, fermentation to36h approach the largest potency and biomass. Established a optimized fed-oil process:5L fermentator feeding soybean oil at12h, during2-3h feeding0.5%soybean oil. In shake flask culture medium which add5g/L glucose, the potency is supreme; the study found that the best time for feeding sugar is8h; At6h feed with2.0%glucose by constant speed, can make the fermentation production cycle prolonged to48h, and the potency activity of culture broth has also improved.The stability research indicated that the antibiotic has strong tolerant to heat, pH and light.The antifungal substance from B. subtilis CGMCC4140has very strong inhibition on C. albicans ATCC64548, and good inhibition some filamentous fungi(A. Niger ATCC20611), pathogenic bacteria (S. aureus ATCC29213E. coli ATCC8739). In addition, the antifungal material has certain inhibition on K. pneumoniae ATCC10031and S. cerevisae ATCC2601, but no inhibition on P. aeruginosa ATCC9027. Analysing inhibition mechanism about candida albicans, it may be the substance inhibit candida albicans chitin synthase, repressing the cell wall formation which need chitinous synthesis, resulting in candida albicans cracking, and stop growth.