Study On Fermentation Process Of Aviromycin Produced By Streptomyces Viridochromogene

Avilamycin is an oligosaccharide antibiotic of the family of phosphatidylcholines,which has the effect of regulating the metabolism of bacteria in the intestine of animals and promoting the growth of animals.Due to its low toxicity,there is no cross-resistance and it is easy to be in the environment.In the degradation,there is almost no residue;at the same time,it has good processing advantages;therefore,avieramycin is considered as a safer veterinary drug additive.Due to the low production of the current production bacteria,and the selection of strains,culture medium and fermentation process is relatively immature,resulting in its industrial production has been limited.In this paper,the fermentation process for the production of aviromycin from Streptomyces viridochromogene was studied.Through the optimization of the selection of the fermentation medium composition and the selection of fermentation conditions,the production of avermectin was greatly increased,and the concept of oxygen carriers was introduced during the fermentation process to enhance the production of avermectin.At the same time,the kinetic model of fed-batch fermentation process of avermectin was established,which provided a theoretical basis for further research and industrialized production.The main findings are as follows:Using Plackett-Burman design,steepest hill climbing method and Box-Behnken center combination design method to optimize the fermentation medium of Streptomyces viridis,the production of amelillin has been significantly improved compared to the original fermentation medium.The initial yield of 210.35 mg/L increased to 270.47 mg/L,an increase of 28.6%,and there was no significant difference from the predicted yield of 270.41 mg/L.Optimized composition of the fermentation medium: glucose 16.17 g/L,sodium chloride 7.5 g/L,corn starch 20.45g/L,manganese chloride 0.6 g/L,ammonium sulfate 4.5 g/L,mannitol 15 g/L,Magnesium sulfate 0.6 g/L,bean cake powder 26.85 g/L,and calcium carbonate 5g/L.The results of single-factor experiments showed that the most suitable species for inoculation was 30 h,inoculation of 6%,rotation speed of 250 rpm,and temperature of 28°C.p H of 7.0.During further exploration of the fermentation process of avermectin,temperature was found to be related to yield and biomass.And the influence of enzyme activity is greater,higher temperature can make the rapid growth of bacteria while increasing the peak biomass in the fermentation,and shorten the fermentation time;low temperature will reduce the peak biomass and production of avermectin,while prolonged Fermentation time;high temperature can increase the activity of glucose-6-phosphate dehydrogenase and succinate dehydrogenase in the fermentation process.The results of single factor experiments showed that the oxygen carriers with good promoting effect were n-hexane,Tween 20 and Tween 80,respectively,and the optimal concentration and addition time of the three oxygen carriers were 3g/L and18h;The composition of the oxygen carrier was further optimized by methods such as the steep hill climbing method and the Box-Behnken center combination design,and the oxygen carrier formulations were 2.72 g/L,2.53 g/L,and 1.95 g/L,respectively.The yield increased from the initial 270.4 to 363.15 mg/L.At the same time,it was found that the oxygen carrier's promoting effect on avermectin was that it increased the biomass and had little effect on the ability to produce a unit cell.In the optimal culture conditions,batch fed-batch fermentation experiments were carried out using the optimized media.The results showed that the production of amelomycin was 0.34 g/L,and at the same time the amelomycin was established.Fermentation kinetic model:...