Isolation and characterization of collagen from the body wall of sea cucumber Stichopus monotuberculatus.

To exploit a new collagen resource from the body wall of tropical sea cucumber, pepsin-solubilized collagen of Stichopus monotuberculatus (PSC-Sm) was isolated and characterized with UV-vis spectra, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), amino acid composition, enzyme-digested peptide maps, Fourier transform infrared spectroscopy (FTIR), maximum transition temperature (Tm ), and solubilities. The maximum absorbance of PSC-Sm was exhibited at 218 nm in UV-vis spectra. The triple helical structure and activity of PSC-Sm could be indicated by FTIR. SDS-PAGE showed that the triple helix of PSC-Sm was formed as (α1 )3 by 3 α1 chain homologous with molecular weight of 137 kDa. The Tm of PSC-Sm and calf skin collagen (CSC) were 30.2 and 35.0 ºC, respectively, which consistent with the result of FTIR that CSC contained more stable triple-helix than PSC-Sm. Peptide maps were different between PSC-Sm and CSC, indicating the differences in their amino acid compositions and sequences. The maximum and minimum solubilities of PSC-Sm were observed at pH 2.0 and 4.0, respectively. A sharp decrease in solubility appeared when NaCl concentration was between 3% and 5%. These results showed that collagen from S. monotuberculatus had the type I collagen characteristics and good thermal stability, and therefore, it could be used as an alternative resource of collagen.