Improve The Production Of Doramectin By Screening Strains

Doramectin is one of the macrocyclic lactones antibiotics and one of avermectins'structural analogues. The bioactivity is similar with avermectin, is one of the most effective parasiticide. Doramectin is a broad-spectum antibiotics, the elimination factor is very low, so it has a broad foreground. This study improved the doramectin by screening high doramectin-producing strains, optimized the fermentation medium by Response Surface Methodology (RSM) and optimized the fermentation conditions, determined the parameters in the process of fermentation and provided the reliable technological parameters for large scale production.First through purification C-1, obtained a stable high-yield strain C-3-8, which was 50% higher than the original strain. It was regarded as an parent strain, which was treated with UV, NS, NTG respectively. The results showed that for the strain C-4-26, NS was the most effective than other methods. Obtained the strain C-6-27 through purifying C-4-26 two generation. The parent strain was named as C-6-27, was treated with sodium cyclohexanearboxylate, streptomycin, kitasamycin, gentamycin, rigamycin and employed NS, finally obtained a high-yield strain C-13-17 and it's production reached 458mg/L, which was 6.6 times higher than that of the ancestral strain C-1.Besides, the fermentation conditions of doramectin were studied in shaking flask. First, we explored the influence of different carbon sources, nitrogen sources, carbon to nitrogen, different volumes and different time of adding precursor on doramectin production. Based on the optimization of carbon source, nitrogen source and carbon to nitrogen, confirmed the best concentration of fermentation medium by employing RSM. Corn starch 108(g/L), composite nitrogen (cotton flour and peptone) 21(g/L),α-amylase 0.2(g/L), calcium carbonate 7(g/L).In addition, we researched the fermentation temperature, the container of shaking flask, the time of seed and the volum of vaccination, then found that the container of 25 ml, pH value of 7.0, the vaccination of 8%, 28℃, fermentation of 13 days, the production of doramectin was the most highest. At the same time, researched the metabolic curve of doramectin in the fermentation, excluded the variational of pH value, total sugar, deoxidize sugar, amino nitrogen and packed cell volume.