Single-layer BSA-NH<sub>2</sub>/PNIPAAm membrane with modulated lipase biocatalytic reaction

Abstract

Biocatalysis, utilizing enzymes or live microbial cultures to catalyze or speed up specific or cascade reactions, has broad applications in the manufacturing of fine chemicals, pharmaceuticals, and agrochemical intermediates. However, how to effectively adjust the biocatalytic process and the dose of enzymes during the reaction becomes one intriguing issue to be addressed. Smart porous membranes are desirable candidates for regulating substance permeability, which provides the possibility to adjust the biocatalysis. Herein, inspired by the temperature-sensitive stomatal size of plant leaves, we prepare a free-standing single-layer membrane through the self-assembly at oil-water interface, which is composed of thermosensitive amphiphilic protein-polymer conjugates, i.e., BSA-NH2/PNIPAAm (poly(N-isopropylacrylamide)). The membrane thickness is only about 4 nm, with a wide range of molecular cut-offs by tuning the molecular weight of PNIPAAm. Moreover, by virtue of the property of PNIPAAm, the pore size of the membrane could be tunable by changing temperature, through which the catalytic reaction of triglyceride by lipase was successfully controlled. Taken together, this work not only provides a simple method for preparing single-layer protein hybrid membranes, but also offers great potential applications in the controlled biocatalysis, smart gating systems and molecular separation.