N-doped hollow porous carbon materials have attracted significant scientific interest in the field of peptide adsorption, drug delivery and catalysis. However, their facile synthesis is still a challenge due to the lack of an ideal template and effective route for high specific surface area (SSA). In this work, we report a facile approach for preparing N-doped hollow porous carbon whiskers (HPCWs) by using CaCO3 whiskers as a green template and double inner-activating agent. Two inner activators, CO2 and Ca(OH)2, are generated from the CaCO3 whisker template during the carbonization process. Among them, Ca(OH)2 was formed by H2O vapors reacting with the remaining template CaO. Attributed to the drastic synergistic effect of inner-activation (CO2 or Ca(OH)2) and outer-activation (KOH), the synthesized HPCWs exhibit ultrahigh SSA (3007 m2 g−1), the largest pore volume (2.63 cm3 g−1) and a controllable proportion of micropores (Sm/St, 60–86%). These intriguing pore structure characteristics of HPCWs endow with them rich target-oriented applications, as exemplified by their outstanding adsorption for casein hydrolysate (10 080 mg g−1), which is two orders of magnitude (102) higher than that of common porous materials. This facile and green synthesis strategy may pave a new way to prepare hollow porous carbon materials with the desired pore structure and high surface area for numerous applications.

•Rapid separation was achieved by application of a magnetic field.•ACE was immobilized on magnetic agarose microspheres as magnetic affinity medium.•The magnetic affinity medium was applied to separate ACE inhibitory peptide.•A new ACE inhibitory peptide was identified.•Magnetic affinity technology can advantageously be applied due to its magnetism.In this study, angiotensin converting enzyme (ACE) inhibitory peptides from lizard fish protein hydrolysate with neutral protease were purified through magnetic affinity separation. Magnetic agarose microsphere was prepared by reverse-phase microemulsion method, and its surface was modified with epoxy groups to immobilize ACE as a magnetic affinity medium (MAM-ACE) and then mixed with lizard fish ultrafiltration hydrolysate (<5 kDa). The MAM-ACE was recovered by a magnet. The bound peptides were released by 1 M NaCl and further purified by reverse-phase high-performance liquid chromatography. The amino acid sequence of the peptide with the highest ACE inhibitory activity was identified as Gly-Met-Lys-Cys-Ala-Phe, and its IC50 was 45.7 ± 1.1 μM. The result indicates that MAM-ACE is a faster and more efficient method for purifying micro-bioactive peptides from food protein complex mixtures compared with ion exchange and gel chromatography.

Muscle protein from round scad (Decapterus maruadsi) was hydrolyzed with five commercial proteases, namely, Alcalase, neutral protease, papain, pepsin, and trypsin. Round scad hydrolysate (RSH) prepared with Alcalase demonstrated high antioxidative activity. After ultrafiltration, RSH-III fraction (MW < 5 kDa) exhibited the strongest activity. Then, RSH-III was purified by gel filtration chromatography (Sephadex G-15) and separated into four fractions (A, B, C, and D), of which fraction B showed the highest antioxidative activity and was further purified using reverse-phase high-performance liquid chromatography twice. The purified peptides were identified as His-Asp-His-Pro-Val-Cys (706.8 Da) and His-Glu-Lys-Val-Cys (614.7 Da) by matrix-assisted laser desorption ionization time-of-flight/time-of-flight mass spectrometry. Subsequently, the identified peptides were synthesized, and their antioxidative activities were verified. Results indicated that the two novel peptides isolated from round scad muscle protein can be developed into antioxidative ingredients in functional foods.Highlights•Two antioxidative peptides, HDHPVC and HEKVC, were isolated from round scad muscle.•Round scad protein was hydrolyzed by Alcalase, purified by different chromatographic methods.•Two peptides were synthesized and their antioxidative activities were estimated.