Bioinspired proteolytic membrane (BPM) with bilayer pepsin structure for protein hydrolysis

Peptides derived from food proteins exhibit a great application potential as natural health product. Conventional enzymatic membrane reactor for peptides production bears some disadvantages, such as high membrane fouling, clear enzyme leaching, and low operational stability. Herein, the bioinspired proteolytic membrane (BPM) with bilayer pepsin structure was fabricated to produce the peptides via reverse filtration and layered immobilization (polydopamine coating and polyethyleneimine grafting). The results of Fourier transform infrared spectroscopy and Emission scanning electron microscopy found that BPM could stably form 3 different structures by various fabrication methods: monolayer reverse proteolytic membrane (MR-PM), monolayer reverse bioinspired proteolytic membrane (MR-BPM) and bilayer reverse bioinspired proteolytic membrane (BR-BPM). Besides, with the increase of enzyme layers, the enzyme loading, enzyme activity and degree of hydrolysis BPM considerably improved. Then, BR-BPM filtration tests were conducted under various operation conditions (transmembrane pressure (TMP) (1–4 bar) and pepsin concentration (0.1–0.9 mg/mL)). BR-BPM acquired the higher enzyme loading, degree of hydrolysis (DH) and permeate flux than MR-PM and MR-BPM by bilayer pepsin structure. In addition, BR-BPM demonstrated the great filtration performance (permeate flux = 6.5 L m −2  h −1  bar −1 and DH  = 45.7%) for the long-term tests (four continuous filtration cycles) at the optimized condition (TMP = 3 bar and pepsin concentration = 0.5 mg/mL). This work offers a promising guideline of the fabrication of functional membrane for peptides production.