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

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>10kDa; CSP2, 6kDa<MW<10kDa; CSP3, MW<6kDa) 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.