Enzymatic membrane bioreactors (EMBRs), with synergistic catalysis-separation performance, have increasingly been used for practical applications. Generally, the membrane properties, particularly the pore structures and interface interactions, have a significant impact on the catalytic efficiency of the EMBR. Therefore, a biomimetic interface based on a phospholipid assembled onto a polysulfone hollow-fiber membrane with perfect radial gradient pores (RGM-PSF) has been prepared in this work to construct a highly efficient and stable EMBR. On account of the special pore structure of the RGM-PSF with the apertures decreasing gradually from the inner side to the outer side, the enzyme molecules could be evenly distributed on the three-dimensional skeleton of the membrane. In addition, the supported phospholipid layer in the membrane, prepared by physical adsorption, was used for the immobilization of the enzymes, which provides sufficient linkage to prevent the enzymes from leaching but also accommodates as many enzyme molecules as possible to retain high bioactivity. The properties of the EMBR were studied by using lipase from Candida rugosa for the hydrolysis of glycerol triacetate as a model. Energy-dispersive X-ray and circular dichroism spectroscopy were employed to observe the effect of lecithin on the membrane and structure changes in the enzyme, respectively. The operational conditions were investigated to optimize the performance of the EMBR by testing substrate concentrations from 0.05 to 0.25 M, membrane fluxes from 25.5 to 350.0 L·m−2·h−1, and temperatures from 15 to 55 °C. As a result, the obtained EMBR showed a desirable performance with 42% improved enzymatic activity and 78% improved catalytic efficiency relative to the unmodified membrane.

Cyclodextrins (CDs) are a family of cyclic oligosaccharides, whose unique hydrophilic outer surface and lipophilic central cavity facilitate the formation of inclusion complexes with various biomolecules, such as cholesterol and phospholipids, via multi-interactions. Low-density lipoprotein (LDL) is the main carrier of cholesterol in bloodstream and is associated with the progression of atherosclerosis. The surface of LDL is composed of a shell of phospholipids monolayer containing most of the free unesterified cholesterol as well as the single copy of apolipoprotein B-100. To date, various LDL adsorbents have been fabricated to interact with the biomolecules on LDL surface. Owing to its elegant structure, CD is considered to be a promising choice for preparation of more economical and effective LDL-adsorbing materials. Therefore, in this study, interaction between β-CD and LDL in solution was investigated by dynamic light scattering, circular dichroism, and ultraviolet spectroscopy. Further, a supramolecular surface based on β-CD was simply prepared by self-assembled monolayer on gold surface. The effect of hydrogen bond and the cavity of β-CD on the interaction between β-CD and LDL was particularly explored by surface plasmon resonance (SPR) analysis. The SPR results showed that such β-CD-modified surface exhibited good selectivity and could be largely regenerated by sodium dodecyl sulfate wash. This study may extend the understanding of the interaction between LDL and LDL adsorbent or the design and development of more efficient and lower-cost LDL adsorbents in the future.

The critical breakthrough pressure related to the membrane surface wettability and pore size is a key parameter determining membrane performance in particular applications, such as oil-water mixture separations. A series of hydrophilic polysulfone hollowfiber membranes with different pore sizes were prepared and characterized to evaluate the separation performance of oil-in-water emulsions and to develop an optimum membrane for such emulsions. For the optimum membrane, the absolute value for the cosine of the surface oil droplet contact angle (0.72) was close to the ratio of the outer surface pore size to the oil droplet size (0.71); it was also similar to the absolute value of the cosine of the underwater oil contact angle on the polysulfone material (0.65). From the point of view of the surface wettability, theoretical calculations were performed to select a suitable membrane with the aim of reaching the maximum efficiency in practical oil-water mixture separation.

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