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Polymyxin also known colistin, Kristin (colistin), polymyxin E (Polymyxin E), against the enemy and other factors, is by multiple Colistin culture liquid obtained in alkaline Suo cyclic peptide (polypeptide ) antibiotics of polymyxin E 1 and E of 2 mixture. White crystal or crystalline powder, slightly soluble in water, is not easy to deliquescence. Its sulfate-polymyxin sulfate nature is very stable, as a white powder, soluble in water, slightly soluble in methanol, ethanol, and insoluble in acetone, ether. Fairly stable in the pH value within 2-6. Heat-resistant, gastrointestinal absorption is not easy, rapid excretion, toxicity, no side effects, is not easy to produce drug-resistant strains, is the safest livestock growth-promoting antibiotics one. Of the subject according to the characteristics of the biosynthesis of the colistin sulfate, the use of UV irradiation to an NTG mutagenesis and anti structural analogues of α-amino butyric acid, by means of strain selection. To the the Bacillus polymyxa class of Paenibacillus polymyxa 6 # as the original strain after UV Mutation Breeding to obtain a stable performance of a genetic sulfate polymyxin fermentation units than the original strain improve 15% of the new strain of 37 # . Then this strain nitrosoguanidine (NTG) mutagenesis as a screening factor aminobutyric acid valine structural analogues and a new increase in production of 18% strains 42 # , this new high-yield strains in shake flasks under the conditions of the process were. To main content, including seeds incubation time, inoculum size, initial pH, culture temperature, carbon source, a nitrogen source, C / N ratio to be optimized to determine the optimal medium C source of glucose 10% and starch 90% The composite C sources, N sources as wheat germ powder with an organic N source of the inorganic N source ammonium sulfate 0.1% 0.3% a combination of complex N source C sources, N sources optimum ratio of 2.5:1. Seed culture time is 20 to 24 hours, and the most suitable inoculation amount was 6%, and the initial pH is controlled at 6.4 ~ 6.6. 18 tons fermenter flask test on the basis of further large-scale production test. Fermentation cycle is fixed in the case of 40 hours to determine suitable ventilation gas ratio is 0.8m 3 / m 3 min, stirring speed of 150rpm, antibiotic synthesis Cultivation The optimum temperature of 33 ° C. Fermentation titer fermentation big tank test results # strains increased by 33%, the volume increased by 6%, to good effect.
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