Dual-gating pH-responsive membranes with the heterogeneous structure for whey protein fractionation

doi:10.1016/j.memsci.2021.119849

Journal of Membrane Science

Volume 641, 1 January 2022, 119849

https://doi.org/10.1016/j.memsci.2021.119849 Get rights and content

Highlights

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Dual-gating pH-responsive EVAL membrane was fabricated for whey protein fractionation.
•
Heterogeneous structure was obtained based on selective modification of grafting sites.
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Multistage regulation of the membrane properties was exhibited.
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Whey protein fractionation from the mixture was achieved via single membrane.

Abstract

Whey protein is a mixture of globular proteins with high nutritional value and excellent functional properties availability. Purified individual whey proteins exhibit better functionality than in their original mixture, thus there is an increasing interest in developing more efficient methods to recover individual whey protein fractions, especially membrane technology. However, whey protein fractionation from the protein mixture is still a huge challenge for membrane separation. Herein, a dual-gating pHresponsive membrane with the heterogeneous structure was developed for whey protein fractionation. The heterogeneous structure of the membranes was obtained by grafting the dimethylaminoethyl methacrylate (DMAEMA) and 4-vinylpyridine (4VP) near the topside and inside the pores of the ethylene vinyl alcohol copolymer (EVAL) membranes based on selective modification of grafting sites. The PDMAEMA and P4VP gates responded to pH individually and provided a multi-stage regulation of the surface charge and sieving property of the membranes. The major whey protein fractionation from the mixture could be achieved by single dual-gating pH-responsive membrane via the sequential stepwise pH gradient from 3.0 to 8.0. The α-Lactalbumin (α-La), β-Lactoglobulin (β-Lg), lactoferrin (LF) and bovine serum albumin (BSA) were separated and enriched in the permeate at pH 3.0, 4.2, 6.4 and 8.0 by the diafiltration process, respectively. This work not only proposed a novel concept of pHresponsive membrane, but also offered a sustainable solution to fractionate the whey protein from the complicated mixture.

Graphical abstract

Section snippets

Author statement

Hui Ye: Conceptualization, Writing-Reviewing and Editing. Chuan Gao: Investigation, Writing-Original draft preparation. Guodong Yang: Visualization, Data curation. Yining Zhou: Investigation. Rui Jiao: Data curation. Yuzhong Zhang: Funding acquisition. Lizhi Zhao: Supervision. Qingping Xin: Investigation. Hong Li: Project administration.

Materials

EVAL (ethylene content 44 mol %) was purchased from Kuraray. Dimethysulfoxide (DMSO) was purchased from Kemiou Chemical Reagents Co., Ltd as the EVAL solvent. 1-octanol, which was employed as a nonsolvent additive, was purchased from Guangfu Chemical Reagents Co., Ltd. DMAEMA and 4VP were obtained from J&K Chemicals and distilled before usage under reduced pressure. Benzophenone (BP) was used as initiator and purchased from TCI. The α-La, β-Lg, LF and BSA were sourced from Sigma-Aldrich.

Single-sided BP immobilization

The dual-gating pH-responsive membrane (DGPRM) was fabricated via photografting, including the BP immobilization and polymer grafting (Scheme 2), thus the BP location played a significant role in establishing the heterogeneous structure of the membranes. The controllable distribution of grafting location has been investigated in our previous work [29]. The higher local BP concentration on the UV-facing side of the membrane, the less UV light transmitted through the membrane, and then the BP

Conclusion

In this work, a dual-gating pH-responsive membrane with the heterogeneous structure was designed and fabricated for whey protein fractionation. The single-sided BP immobilization was achieved based on the UV absorbability of BP, as well as the BP migration during the acetone evaporation. The PDMAEMA and P4VP chains, which acted as the dual gates, were grafted near the topside and inside the pores of the membranes to obtain the heterogeneous structure of the EVAL membranes. The dual-gating

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors acknowledge the National Key Research and Development Plan (2017YFC0404001), National Natural Science Foundation of China (No. 21978217, 21706189 and 21676201), National college students' innovative entrepreneurial training plan (202110058065), Natural Science Foundation of Tianjin Municipal Science and Technology Commission (14JCQNJC03900 and 18JCQNJC06800), as well as Tianjin Natural Science Foundation (18JCYBJC89400).

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Dual-gating pH-responsive membranes with the heterogeneous structure for whey protein fractionation

Highlights

Abstract

Graphical abstract

Section snippets

Author statement

Materials

Single-sided BP immobilization

Conclusion

Declaration of competing interest

Acknowledgements

Int. Dairy J.

J. Food Eng.

Biotechnol. Adv.

Separ. Purif. Technol.

Food Chem.

J. Food Eng.

Separ. Purif. Technol.

J. Membr. Sci.

Adv. Colloid Interface Sci.

J. Membr. Sci.

J. Membr. Sci.

J. Membr. Sci.

J. Chromatogr. A

J. Membr. Sci.

J. Membr. Sci.

J. Chromatogr. A

J. Colloid Interface Sci.

Acta Biomater.

J. Membr. Sci.