Screening, identification and degradation characteristics of tetracycline-degrading strains | 四环素降解菌的选育、鉴定及其降解特性

中国人. 生产四环素过程中产生大量发酵底物(俗称“药渣”)，采用生物二次发酵法可消除药渣中四环素，使其能作为饲料原料使用。本研究从长期堆放四环素药渣的土壤中筛选四环素降解菌株，经驯化富集后筛选得到TD2和TD3两株能高效降解四环素的菌株。根据表型特征、生理生化特性及16S rDNA序列同源性分析，鉴定TD2为缺陷短波单胞菌(Brevundimonas diminuta)，TD3为人苍白杆菌(Ochrobactrum anthropi)。TD2和TD3均可利用四环素作为碳源生长。TD2在碳源、氮源、矿物质分别为无碳源、蛋白胨0.5%、CuSO4 0.015%时，降解性能最优；而TD3在葡萄糖0.5%、牛肉膏1.5%、CuSO4 0.015%的培养基中降解效率最大。两株菌的最适培养条件相同：培养时间5 d、温度30 ℃、接种量1%，且四环素降解率与通气量成正相关。在最适条件下，TD2和TD3的四环素降解率均达90%以上。本实验筛选所得的两株四环素降解菌株可作为四环素药渣进行二次发酵的候选菌株。

英语. Tetracycline waste residue is considered to be a good protein source for animal feed, since it contains a high proportion of protein and a relatively nutritional balance in amino acids composition. On the other hand, tetracycline waste residue also has a high level of tetracycline, which will limit its usage in animal feed industry. It may be feasible to eliminate tetracycline in the waste via microorganism fermentation method. Thus, the present study was conducted to obtain tetracycline-degrading strains. Two tetracycline-degrading strains, named TD2 and TD3, were isolated from soil contaminated by tetracycline. Based on the results of phenotype features, physio-biochemical identification and the phylogenetical analyses of 16S rDNA sequence, TD2 and TD3 were identified to Brevundimonas diminuta and Ochrobactrum anthropi, respectively. Both TD2 and TD3 could grow in the medium containing tetracycline as only carbon source. The highest efficacy of TD2 was achieved when it was incubated in the medium consisted of 0.5% peptone and 0.015% CuSO4, whereas that of TD3 was obtained in the medium composed of 0.5% glucose, 1.5% beef extract, 0.015% CuSO4. Identically, both TD2 and TD3 had an optimal inoculation ratio of 1%, and tetracycline degradation rate proportional to ventilation, as well as an optimal culture condition of 30℃ for five days. After the optimal incubation, the tetracycline degradation ratio for the two strains could be up to 90%. Our results indicated that TD2 and TD3 were the microorganism candidates for the tetracycline waste residue fermentation process by which tetracycline can be eliminated.