Preparation of cucumber seed peptide-calcium chelate by liquid state fermentation and its characterization

•An extraction process was found to produce a specific peptide from cucumber seed.•The calcium-chelating ability of different peptide components was evaluated.•The differences of characterization between CSP3 and CSP3-Ca chelate were given.

A specific cucumber seed peptide (CSP) was successfully produced by liquid state fermentation with B. subtilis HYT. Then the CSP was divided into four kind molecular weight components (CSP, untreated; CSP1, MW > 10 kDa; CSP2, 6 kDa < MW < 10 kDa; CSP3, MW < 6 kDa) by ultrafiltration. Among them, the CSP3 displayed the most excellent ability to chelate with calcium (CSP3-Ca). SEM, EDS, ultra-violet spectroscopy, FTIR and Fluorescence spectroscopy were applied to distinguish the characterizations between CSP3 and CSP3-Ca chelate. The results suggested that the apparent characteristics and internal structure of CSP3 were both changed. There were abundant mental-binding sites presented in CSP3, and the COOH, OH, NH2 as well CONH might participate in the coordination with Ca2+ to form the CSP3-Ca chelate. Meanwhile, the finding showed that cucumber seeds peptide could chelate with calcium and play the role of novel carries for calcium supplement.