Table 2.

Enzymatic hydrolysis of plant and microbial protein to prepare calcium peptide chelate

Protein source	Types of proteases	Peptide: CaCl2 ratio	Chelating reaction conditions	Identified peptide sequence	Binding site (group)	Bioavailability assay	References
Lemon basil seeds	Alcalase	0.5 mg/mL protein hydrolysates to 1 mL of 9 mM CaCl2	Stirring (pH 7.5, 37 °C,150 rpm, 2 h); centrifugation (15,900 g, 10 min)	AFNRAKSKALEN; YDSSGGPTPWLSPY	Amino nitrogen atoms and the oxygen atoms on the carboxyl group	Caco-2 cell monolayers	(Kheeree et al., 2022)
Schizochytrium sp.	Alcalase, favourzyme	/	/	YL	Carboxyl oxygen atoms, amino nitrogen atoms, the nitrogen and oxygen atoms of amide bonds	Caco-2 cell monolayers	(Cai et al., 2017b)
Sunflower seed; peanut	Pepsin, trypsin	1:3.33 mass ratio	Incubation (30 min); add ethanol; centrifugation (2268 g, 20 min)	Peptide contains a large number of characteristic amino acid sequences	Carboxyl and amino groups	Caco-2 cell monolayers	(Bao et al., 2021a)
Manchurian walnut	Alcalase	3:1 mass ratio	pH 8, 40 min, 45 °C	/	Amino nitrogen atoms, carboxyl groups and the C=O of the peptide bond which has a negative dipole	Simulate gastrointestinal digestion in vitro	(Fang et al., 2020)