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. 2025 Sep 4;17(17):2409.
doi: 10.3390/polym17172409.

Fabrication of Zein Nanoparticle-Functionalized Wheat Gluten Amyloid Fibril/Methyl Cellulose Hybrid Membranes with Efficient Performance for Water-in-Oil Emulsion Separation

You-Ren Lai  1 , Jun-Ying Lin  1 , Jou-Ting Hsu  1 , Ta-Hsien Lin  2 , Su-Chun How  3 , Steven S-S Wang  1
Affiliations

Fabrication of Zein Nanoparticle-Functionalized Wheat Gluten Amyloid Fibril/Methyl Cellulose Hybrid Membranes with Efficient Performance for Water-in-Oil Emulsion Separation

You-Ren Lai et al. Polymers (Basel). .

Abstract

Considering the high stability of water-in-oil (W/O) emulsions, contamination from emulsified pollutants poses a long-term risk to the environment. In this study, hybrid membranes composed of wheat gluten amyloid fibrils (WGAFs) and zein nanoparticles (ZNPs) were prepared and used as a separator to remove emulsified W/O droplets from the oily phase. ZNPs and WGAFs were synthesized through antisolvent method and fibrillation process. Next, a ZNP-functionalized wheat gluten AF/methyl cellulose (ZNP-WGAF/MC) hybrid membrane was fabricated, and its properties were investigated via various analytical techniques. Lastly, the separation efficiency of the ZNP-WGAF/MC hybrid membrane for various W/O emulsions was assessed using microscopy and light scattering. The formation of ZNPs or WGAFs was first verified via spectroscopic and microscopic methods. Our results indicated that the ZNP-WGAF/MC hybrid membranes were synthesized via chemical crosslinking coupled with the casting method. Furthermore, the incorporation of either WGAFs or ZNPs was found to improve the thermal stability and surface hydrophobicity of membranes. Finally, the separation efficiency of the ZNP-WGAF/MC hybrid membranes for various W/O emulsions was determined to be ~87-99%. This research demonstrates the potential of harnessing three-dimensional membranes composed of plant protein-based fibrils and nanoparticles to separate emulsified W/O mixtures.

Keywords: amyloid fibril; emulsion separation; nanoparticle; three-dimensional membrane; wheat gluten; zein.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
(A) Hydrodynamic size distribution of ZNPs. (B) SEM micrograph of ZNPs. (Scale bar = 1 μm) TEM micrograph of ZNPs at magnifications of (C) 100 k× and (D) 200 k×. (E) Diameter distribution of ZNPs as analyzed by ImageJ.
Figure 2
Figure 2
(A) ThT fluorescence spectra of WGAFs at different incubation times (excitation wavelength = 440 nm). (B) ThT fluorescence intensity at an emission wavelength of 485 nm of WGAFs as a function of incubation times. FTIR deconvolution spectra of (C) wheat gluten monomers and (D) WGAFs. (E) TEM micrograph of WGAFs (Scale bar = 100 nm). (F) Width distribution of WGAFs as analyzed by ImageJ.
Figure 3
Figure 3
(A) FTIR spectra of wheat gluten monomers, MC, WGAFs, and ZNPs. (B) ATR-FTIR spectra of MC membrane, WGAF/MC hybrid membrane, and ZNP-WGAF/MC hybrid membrane. (C) TGA and (D) DTG curves of MC membrane, WGAF/MC hybrid membrane, and ZNP-WGAF/MC hybrid membrane.
Figure 4
Figure 4
(A) Physical appearances and thickness of MC membrane, WGAF/MC hybrid membrane, and ZNP-WGAF/MC hybrid membrane. (B) Top-view SEM micrographs of MC membrane, WGAF/MC hybrid membrane, and ZNP-WGAF/MC hybrid membrane. SEM images were taken at magnifications of 100× (left panel) and 3000× (right panel). (C) Side-view SEM micrographs of MC membrane, WGAF/MC hybrid membrane, and ZNP-WGAF/MC hybrid membrane. SEM images were taken at magnifications of 3000×. (D) Water contact angles of MC membrane, WGAF/MC hybrid membrane, and ZNP-WGAF/MC hybrid membrane. (Different lowercase letters above bars show significant differences (p < 0.05)).
Figure 5
Figure 5
(A) Physical appearances and (B) optical micrographs of various W/O emulsions before and after filtration through WGAF/MC hybrid membrane and ZNP-WGAF/MC hybrid membrane. (GOL: gasoline, DSO: diesel oil, SBO: soybean oil, SFO: sunflower oil, and GRO: gear oil) Hydrodynamic size distributions of the (C) W/DSO emulsion and (D) W/GRO emulsion before and after filtration through WGAF/MC hybrid membrane and ZNP-WGAF/MC hybrid membrane. (E) Separation performances of the WGAF/MC hybrid membrane and ZNP-WGAF/MC hybrid membrane for various emulsified W/O droplets. (F) Water contact angles of the WGAF/MC hybrid membrane and ZNP-WGAF/MC hybrid membrane before and after filtering emulsified W/DSO mixtures. (Different lowercase letters above bars show significant differences (p < 0.05)).
Figure 5
Figure 5
(A) Physical appearances and (B) optical micrographs of various W/O emulsions before and after filtration through WGAF/MC hybrid membrane and ZNP-WGAF/MC hybrid membrane. (GOL: gasoline, DSO: diesel oil, SBO: soybean oil, SFO: sunflower oil, and GRO: gear oil) Hydrodynamic size distributions of the (C) W/DSO emulsion and (D) W/GRO emulsion before and after filtration through WGAF/MC hybrid membrane and ZNP-WGAF/MC hybrid membrane. (E) Separation performances of the WGAF/MC hybrid membrane and ZNP-WGAF/MC hybrid membrane for various emulsified W/O droplets. (F) Water contact angles of the WGAF/MC hybrid membrane and ZNP-WGAF/MC hybrid membrane before and after filtering emulsified W/DSO mixtures. (Different lowercase letters above bars show significant differences (p < 0.05)).
Figure 6
Figure 6
(A) Separation performances of the MC, MC-1, WGAF/MC-1, and ZNP-WGAF/MC membranes for various emulsified W/O droplets (The capital letter T denotes membrane thickness) (Different lowercase letters above bars show significant differences (p < 0.05)). (B) Correlation between the membrane composition and properties with emulsion separation efficiency, as determined using Pearson correlation coefficients.
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