Single-layer Protein Polymer Membrane For Modulating Biocatalytic Reactions

Biocatalysis,utilizing enzymes or live microbial cultures to catalyze or speed up specific cascade reactions,has broad applications in the manufacturing of fine chemicals,pharmaceuticals,and agrochemical intermediates.However,how to effectively adjust the biocatalytic process becomes one intriguing issue to be addressed.Smart membranes are desirable candidates for regulating substance permeability,which provides the possibility to adjust the biocatalysis.Herein,we prepared a single-layer membrane through the self-assembly of thermosensitive amphiphilic protein-polymer conjugates,i.e.,（poly（N-isopropylacrylamide））at the oil-water interface.By changing the molecular weight of the polymer and the ambient temperature,the molecular weight cutoff of the membrane can be adjusted.The precise control of enzyme reaction is realized by using the programmed change of temperature.The detailed research contents are listed as follows:Firstly,the degree of amination of the element intermediate BSA-NH₂ and the degree of polymer coupling in the protein-polymer conjugate（BSA/NH₂-PNIPAAm）were determined by the ultraviolet/visible spectrometer.The hydrophilicity and hydrophobicity on both sides of the protein polymer membrane were discussed,confirming its Janus structure,which was prepared by the method of self-assembly at the oil-water interface.Besides,the protein-polymer membrane has a continuous and stable monolayer structure,which was verified by AFM,SEM,TEM.Furthermore,the relationship between the molecular weight cutoff of protein-polymer monolayer membranes and the molecular weight of polymers was deeply studied.The pore size of protein-polymer monolayer was estimated according to the molecular weight cutoff.It also proved that there is no interaction between the basic element of the protein-polymer monolayer membrane and the fluorescent dye of FITC-DEX（used to determine the molecular weight cutoff when the external environment changes during the experiment）.In addition,based on the temperature responsive property of PNIPAAm,the reaction process of tributyl glyceride catalyzed by lipase was accurately regulated by the on/off status of the membrane hole,thus adjusting the biocatalytic reaction.Taken together,this work not only provided a simple method for preparing single-layer protein hybrid membranes,but also offered great potentials in the field of controlled biocatalysis,smart gating systems and molecular separation.