Abstract

In this study, biodegradation of tetracycline, which is one of the most commonly used antibiotics, was investigated. In order to convert tetracycline into inactive oxidative metabolites, laccase immobilized onto rigid tripolyphosphate-treated chitosan beads was utilized. For immobilization, chitosan surfaces were activated with glutaraldehyde-linker reagents after tripolyphosphate treatment. The glutaraldehyde-linked rigid chitosan beads showed the higher immobilization capacity of laccase, providing thermostability, reusability, and the higher tetracycline transformation activity. Subsequently, synthetic mediators, including 2,2'‑azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and lignophenolic mediators like violuric, syringic and ferulic acids, 1-hydroxybenzotriazole, and vanillin, were investigated to activate laccase as electron mediators with KI assistance. Among them, the immobilized laccase showed highest tetracycline antibiotic inactivation activity when ABTS was used as a mediator. In the presence of KI, violuric and ferulic acids, 1-hydroxybenzotriazole and vanillin functioned as laccase mediators and inactivated tetracycline almost completely, however, the effect was not observed when they did individually. Finally, V_max of the immobilized laccase was determined as 76.3 ± 4.3 µmoles mg^–1 min^–1 against tetracycline, which was 2-fold higher than that of the free enzyme. These results will provide novel insights into laccase-based removal of non-biodegradable organic matter.

中文翻译：

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固定在壳聚糖-三聚磷酸酯珠上的漆酶生物催化剂对四环素类抗生素的生物降解

摘要

在这项研究中，研究了最常用的抗生素之一四环素的生物降解。为了将四环素转化成惰性的氧化代谢物，使用了固定在刚性三聚磷酸酯处理的壳聚糖微珠上的漆酶。为了固定化，在三聚磷酸盐处理之后，用戊二醛-连接剂活化壳聚糖表面。戊二醛连接的刚性壳聚糖珠粒显示出更高的漆酶固定能力，提供了热稳定性，可重复使用性和更高的四环素转化活性。随后，合成介体，包括2,2'-叠氮基双（3-乙基苯并噻唑啉-6-磺酸）（ABTS）和木质酚介体，如紫，丁香和阿魏酸，1-羟基苯并三唑和香草醛，研究人员在KI辅助下激活漆酶作为电子介体。其中，当以ABTS为介质时，固定化的漆酶显示出最高的四环素抗生素灭活活性。在KI，紫草酸和阿魏酸的存在下，1-羟基苯并三唑和香草醛几乎完全充当漆酶介体和灭活四环素，但是，当它们单独使用时，未观察到效果。最后，固定化漆酶的V _max对四环素的测定值为76.3±4.3 µmoles mg ^–1 min ^–1，比游离酶高2倍。这些结果将为基于漆酶的不可生物降解有机物去除提供新的见解。