Engineering Mussel-Inspired Coating on Membranes for GreenEnzyme Immobilization and Hyperstable Reuse

A mussel-inspired coating based on catecholamine chemistrycan serve as a versatile platform for covalent enzyme immobilization.However, its application was limited by the weak salt/acid/alkali tolerance.To tackle this issue, three silane coupling agents were screened to constructa coating layer on a nylon membrane with tannic acid (TA) for enzymeimmobilization. It was found that TA/3-aminopropyltriethoxysilane(APTES), and TA/3-(2-aminoethylamino) propyltriethoxysilane(AEAPTES) coatings had higher enzyme loading and activity than TA/3-glycidyloxypropyltrimethoxysilane (KH-560), because TA/APTES and TA/AEAPTES coatings formed more nanoparticles and thus provided moreactive sites for enzyme attachment (taking glucose oxidase as an example).Then, the pH tolerance of the immobilized enzyme was greatly enhanced byreinforcing the interfacial interactions of membrane-coating and coating-enzyme, which was realized by membrane pretreatment, ternary additive, and metal ions chelation posttreatment. The optimizedTA/AEAPTES/tetraethoxysilane (TEOS)-Fe3+coating showed excellent pH stability and reusability, and the immobilized enzymeretained 82%, 83%, and 79% of its initial activity even after 7 h of incubation in buffer solutions at pH 3, 7, and 11, respectively. Sucha coating layer was also evaluated for zearalenone hydrolase (ZHD) immobilization, and the immobilized ZHD exhibited boostedactivity and robust reusability in the degradation of zearalenone (ZEN, a refractory and hypertoxic mycotoxin). This work not onlyoffered a green and practical strategy for enzyme immobilization but also provided fundamental data in the design of a mussel-inspired coating layer toward versatile applications