Isolation and characterization of thermostable collagen from the marine eel-fish (Evenchelys macrura)

•Skin waste of eel fish Evenchelys macrura as a cheap source.•Commercially collagen found non-edible and dumped as the waste of fishes.•It is might can be used as an alternative source of natural mammalian collagen.•Isolated collagen is high thermal stability in comparison to the other skin sources.•It is useful for foods, cosmetics, pharmaceuticals commercial industrials export. Collagen is the most abundant protein found in animal body, which is widely used for biomedical and pharmaceutical applications. In the present study, acid soluble collagen (ASC) and pepsin soluble collagen (PSC) from the skin wastes of marine eel fish (Evenchelys macrura) were isolated and characterized. ASC and PSC extracted from eel fish skin showed the yields of 80 and 7.10 percent (based on dry weight), respectively. ASC and PSC comprising different α-chains (α1, α2 and α3) were characterized as type I and exhibited high solubility in acidic pH (1–4) and were soluble in the presence of NaCl at concentration up to 3.0 and 4.0 percent (w/v) for ASC and PSC, respectively. Amino acids analysis of both ASC and PSC contained imino acid of 190 and 200 residues per 1000 residues, respectively. The present results of ASC and PSC from eel fish skin exhibited higher thermal stability of 39°C and 35°C, respectively. Similar, Fourier transform infrared (FTIR) spectra of ASC and PSC were observed and suggesting that pepsin hydrolysis did not affect the secondary structure of collagen, especially triple-helical structure. These results suggest that the marine eel fish skin collagen close to the Td (denaturation temperature) of mammalian collagen which could be used in the biomedical materials, food and pharmaceutical industries as an alternative source.