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

A mussel-inspired coating based on catecholamine chemistry can 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 construct a coating layer on a nylon membrane with tannic acid (TA) for enzyme immobilization. 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 more active sites for enzyme attachment (taking glucose oxidase as an example). Then, the pH tolerance of the immobilized enzyme was greatly enhanced by reinforcing the interfacial interactions of membrane–coating and coating–enzyme, which was realized by membrane pretreatment, ternary additive, and metal ions chelation posttreatment. The optimized TA/AEAPTES/tetraethoxysilane (TEOS)-Fe3+ coating showed excellent pH stability and reusability, and the immobilized enzyme retained 82%, 83%, and 79% of its initial activity even after 7 h of incubation in buffer solutions at pH 3, 7, and 11, respectively. Such a coating layer was also evaluated for zearalenone hydrolase (ZHD) immobilization, and the immobilized ZHD exhibited boosted activity and robust reusability in the degradation of zearalenone (ZEN, a refractory and hypertoxic mycotoxin). This work not only offered 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.