化学氧化与生物降解联合消除药渣残留四环素的机制研究

Ningxia is one of the main producing areas of crude antibiotics in China. Among these, the production scale of tetracycline is the highest in the world. However, a large amount of tetracycline solid waste (TSW) has been generated in the process of tetracycline production. The resource utilization of TSW is restricted greatly because of the existence of residual tetracycline. Moreover, it is one of main causes that lead to accumulation of environmental tetracycline and development of antibiotic resistant microbial populations. In our laboratory, a bacterial strain, which exhibited a strong biodegradability to oxidation intermediates stemmed from tetracycline in pharmaceutical solid waste after treatment with a combination of O3 and NaClO, was isolated and acclimated. In this study, TSW is firstly treated with O3 coupled with NaClO. Meanwhile, the microcosmic essence of the interaction between tetracycline and oxidant is calculated and simulated. This process is to convert the persistent tetracycline into intermediate products which are more easily biodegradable. At the same time, the antibacterial and toxic actions of tetracycline molecule are significantly reduced for subsequent treatment with microorganism. Thereafter, the isolated strain is used to biodegrade the intermediate products from tetracycline after oxidation. The degradation pathway and structural change of tetracycline molecule are dynamically analyzed during the processes of chemical oxidation and biological metabolism. The composition, structure and fate of degradation products are characterized and their environmental safeties are evaluated. The degrading enzyme and its coding gene are separated and investigated. The objectives of these are to ascertain the removal mechanism of tetracycline residue in pharmaceutical solid waste using a combination of chemical oxidation and biodegradation and to get a novel method for complete elimination of tetracycline residue in TSW.

宁夏是我国抗生素原料药主产区之一，其中四环素生产规模居世界首位。但在四环素生产中，产生了大量的废弃药渣，这些药渣因残留四环素的存在，极大地限制了其资源化利用，更重要的是，成为造成环境四环素蓄积、耐药菌泛滥的主要原因之一。本课题组已筛选、驯化到1株对O3/NaClO处理药渣四环素后的氧化中间产物具有高效降解作用的菌株。本项目首先用O3/NaClO耦合处理药渣四环素，并计算和模拟四环素与氧化剂相互作用的微观本质，在将四环素氧化为易被微生物降解代谢的中间产物的同时，大幅度降低其对后续处理微生物的抑菌和毒性作用，然后再用微生物降解四环素氧化后的中间产物，通过对四环素在化学氧化和生物代谢过程中降解途径和结构演变的动态解析，降解产物组成、结构和归趋的表征分析及环境安全性评价，降解酶及其编码基因的分离与研究，探明化学氧化与生物降解联合消除药渣残留四环素的分子机制，并获得完全彻底降解药渣残留四环素的方法。

我国四环素生产规模居世界首位。但在四环素生产中，产生了大量固液废，这些废弃物是造成环境四环素蓄积、耐药菌泛滥的主要原因之一。本项目主要开展了O3/NaClO耦合氧化降解药渣残留四环素的效果与机制、四环素氧化产物的微生物降解途径，降解产物的组成、结构、归趋及环境安全性、降解酶及其编码基因等方面的研究工作。取得的主要成果：（1）NaClO对四环素的氧化降解效果优于O3，二者单独使用都不能完全降解药渣残留的四环素，但二者耦合使用后能实现残留四环素的有效降解。Fe2+对O3氧化有催化效果，其机制是催化促进O3产生OH•。（2）NaClO/O3降解四环素产生了质荷比（m/z）分别为459，477，443，462，415和522的6种氧化产物，降解过程主要基于羟基化、去甲基化、氯代反应等。（3）四环素经H2O2氧化降解过程主要是基于H2O2的直接分子氧化作用，而非OH•氧化机理，四环素降解是通过羟基化，失去官能团（如N-甲基、羟基、羧基），开环等历程。（4）制备出对四环素具有强吸附作用的Cu-13X分子筛吸附剂，最大吸附量达到2428 mg/g，其吸附机理源于四环素分子中酰胺基团与分子筛上Cu2+之间强烈的络合作用。（5）利用原位水热合成法分别制备出了金属氧化物改性膨胀石墨和MnO2/石墨烯，对絮凝后制药废水中四环素的去除率高达99%以上；利用真空抽滤技术分别制备了ZIF-8/GO复合膜和3D ZIF-L复合膜，可直接高效去除制药废水中残留的四环素，去除率均高于99%。（6）四环素膜浆先经Fe2+/O3处理，再加入白腐真菌，残留四环素的降解率可达100%，TOC去除率36.1%。（7）白腐真菌也可对四环素经NaClO/O3降解所得氧化产物进行生物降解，降解产物为质荷比为443的单一化合物。该降解产物经环境毒性测定，其毒性大大低于母体分子。（8）发表学术论文11篇（SCI/EI收录9篇），申请国家发明专利12项，获科研奖励3项，培养研究生9名（已毕业7名，在读2名）。（9）本项目的研究成果对抗生素废弃物的处理有重要的指导意义，而且对环境保护，提高资源循环利用效率，促进经济与环境和谐发展具有重要的社会意义。