Abstract：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.
